A Study in the Comparative Anatomy of the Blood-vascular System of the Internal Ear in Mammalia and in Homo (Japanese).

Transcription

1 From the Anatomical Laboratory of the Imperial University of Kyoto. A Study in the Comparative Anatomy of the Blood-vascular System of the Internal Ear in Mammalia and in Homo (Japanese). By DENJIRO NABEYA. With 16 Plates, 13 Photographs, and I8 Textual figures. (Received for publication, March 31, 1923.) Analysis.

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3 A Study in the Comparative Anatomy of the etc. 3 Investigations preparatory Introduction. to this study were carried out in three places ; first, in the Anatomical Laboratory of the University of Chicago in the U. S., during o, under the guidance of Prof. R. R. BENSLEY and Prof. G. E. SHAMBAUGH, on the guinea-pig, the rabbit, and the cat ; secondly, in the Otological Laboratory of the Imperial University of Tokyo in Japan, under the guidance of Prof. W. OKADA, during 1921, On the dog and the rat ; thirdly, in the Anatomical Laboratory of the Imperial University of Kyoto, under the guidance of Prof. S. WATSUJI, and Prof. B. ADACHI, , on the monkey and man. In the course of this study which has involved a great number of experiments with several kinds of materials, I have acquired a thorough knowledge of the blood-vascularization of the internal ear, for which I am deeply indebted to the above-mentioned instructors. The studies of the guinea-pig, of the rat, of the dog, and of man, have been undertaken by me to confirm certain doubtful points raised by previous investigators, but the studies of the rabbit, of the cat, and of the monkey are almost wholly original. Now, let me give as examples, my results with the arterial and venous trunks in the labyrinth, which are the most important points of this work ; The Arteria auditiva interna which arises directly from the Arteria basilaris, and which is mistakenly described in general textbooks of anatomy and of otology by Siebenmann, Eichler, and others, as extending over the basal brain, actually has no existence. The Arteria labyrinthica, therefore, is always a branch of the Arteria cerebelli inferior anterior which crosses over the porus acusticus internus. The central cochlear vein of the Venae auditivae internae, as to the existence of which Siebenmann and Shambaugh take opposite' views, is non-existent in 304 ears of 152 skulls which were painstakingly given color injection and examined by myself. The result of this

4 4 DENPRO NABEYA venous research quite agrees with the view held by Shambaugh. I shall describe in detail my observations, after first giving my opinion upon the essential point of this problem, and explaining the technic of this research in the next chapter. An essential point for the understanding of the blood-vascular system in the labyrinth. The blood-vascular system in the membranous labyrinth is inter-- woven with that in the endosteum of the bony labyrinth, but it is in no way connected with that in the bony substance I have never found the blood-vessels in the substance of the bony labyrinth, contrary to Siebenmann's descriptions (19 and 20). The dura mater and the arachnoid in the meatus acusticus internus have no systematic connection for forming an identical membranous system with the membranous labyrinth and the endostal wall of the labyrinth. Accordingly, although the meatus acusticus internus is the route of the three main branches * of the labyrinthine artery, N. acusticus and its sheath in thn meatus acusticus internus are distributed in a quite different manner from the labyrinth by many branches of the three main branches of the artery, and by many venous twigs of the Vv. auditvae internae which have no systematic connection with the vessels of the labyrinth. In the labyrinth the blood-vessels run along the endostal surface and branch off very systematically, while in the meatus acusticus internus they run along the stems of the branches of N. acusticus and branch off not so systematically as do the former. The branches in the meatus acusticus internus do not invade the labyrinth, rather some branches run contrariwise going out to some portions of the basal brain. Even Siebenmann's so-called A. nervi ampullaris posterioris, in spite of its running along R. nervi vestibularis posterior, does not penetrate into the labyrinth, therefore, it does not reach the macula cribrosa inferior. Moreover, A. saccularis is not branched off in the meatus acusticus internus, contrary to Siebenmann's observation, but it is given off from the R. vestibularis of A. vestibulo-cochlearis of * A, vestibuli anterior A. vestibulo-cochlearis of A, vestibuli posterior A. cochleae propria,

5 A Study in the comparative Anatomy of the etc. 5 A. vestibuli posterior in the labyrinth, accordingly. it has no relation with the meatus acusticus internus. I shall explain in detail these conditions of the blood vessels later on. At any rate, when we make a careful observation of these portions, we see quite a different system of the blood-vascularization between the meatus acusticus internus and the labyrinth. This is an essential point in deciding some questions, for example, Vv. auditivae internae which are the subject of so much discussion at present. Of course this anatomical relation arises from an embryological cause, but I was deeply impressed by (this) actual observation on this subject, comparing it with the writings of K I BEL (IC) and HERTWIG (9). Method. Two different methods have been employed for my experiments on the mammals, an equal number of them being taken for each method, thus (I) Eichler and Siebenmann's method, recommended by Prof. G. E. SHAMBAUGH. (2) My own method, which is a modification of Spalteholz's method of making transparent specimens (21). (1) I shall first explain my process of making the specimen by the former method. Each of the above mentioned authors described their use of the first method as applied to their own studies it is a very interesting study in technique to compare them with mine sence a considerable familiarity with the first method is necessary in the use of the various materials according to my own method. a) I used 1-3 / Prussian blue solution which is a simple water solution as the coloured stuff to be injected into the blood-vascular system of all my subjects of examination, namely men and other mammals, excepting two of the men and eight of the mammals with which I tried the injection of Indian ink. According to the results of my experiments, a 2 % Prussian blue solution is the best colour stuff for my purpose, for it gives a beautiful and clear view under the microscope of the specimens of any mammal, while Indian ink gives a dark view under the microscope P which renders it difficult clearly to see that portion of the complex dist ribution of the blood-vessels which lie one above the other. TATSUMI and KURODA of the Medical College of Osaka, made a

6 6 DENJIRO NABEYA report before the Otological Section of the General Meeting of Japanese Medical Societies (1922), saying that a new stuff for injections in this kind of research, i. e., the ink of the cuttle-fish, obtained good results in making specimens of the blood-vascular system in the membranous labyrinth of some kinds of mammals, for example, the cat, or the guinea-pig. However, I do not think that it is much better than the Prussian blue solution ; but I do not hesitate to suggest one way in which it could be used to advantage. When used side by side with the Prussian blue solution it might attract our fresh attention to some unobserved portion by the stimulation of a different colour, on our sight. I repeat, however, that it is by no means indispedsable for this work. b) The portion of the blood-vessels T selected for the injection of a colour solution was treated as follows : For small animals like rats I made an injection with c.c. of the solution directly through the heart ; for monkeys, guinea-pigs, rabbits, dogs, and cats, lop woo c.c. of the solution through the common carotid artery ; for the cadavers of men I took two different portions of the arterial system and employed a large dose of about sood c.c. of the solution, first, I made the injection through the internal carotid artery with 4000 c.c. of the solution ; secondly, through the vertebral artery again with I ODO c.c. of the solution ; but for the fetus and the baby, however, I made a satisfactory injection with 1030 c.c. of the solution into only one portion, namely, the internal carotid or the common carotid artery. c) In making an injection into the living body of an animal, the following precaution should be taken : The animal has to be held in a restful state by means of aether anaesthesia, and while in that condition let it bleed as much as possible. Then, and as soon as possible, the common carotid artery or the internal carotid attery, or sometimes its heart, should be exposed to view by means of a wide incision made upon a portion of the neck or by opening the breast, and then a small incision should be made in the artery or the heart through which to insert the glass canula connected with the injecting apparatus by means of a long rubbertube. The size of this glass canula must be of a dimension corresponding to the size of the blood-vessel of each mammal into which it is to be inserted. To the case of the cadaver of man, I previously cut the skull off

7 A Study in the comparative Anatomy of the etc. 7 from the body and obligated all the blood-vessels on the cut surface of the neck, excepting the internal jugular vein on both sides. These are left open to let the injected solution run out, but from time to time they must be stopped by using the haemostatic forceps to force the colour solution to fill blood-vessels in the skull. I made, thereupon, the injection into the internal carotid artery on one side of the neck and when the dose injected reached 2000 c.c., I transferred the injection to the artery of the other side, giving it the same dose of the colour solution. Lastly, the same injection of 500 c.c. in each was repeated into the vertebral artery on both sides. With the cadaver of the baby or the foetus, I made the injection immediately into the internal or common carotid artery without cutting off the neck, but opening the internal jugular vein by means of a small incision for an exit of the injected solution. When the injected 'olution reached about 500 c.c. I repeated an injection of the same dose of the colour solution into the vessel on the other side. d) It is best to use static pressure in the injection, the elevation being some 4--7 feet. This elevation, of course, has to be arranged according to the size of materials ; for example, about four feet for the guinea-pig, about six feet for the dog, and about seven feet for an adult human being. According to my experience, this arrangement is very convenient for handling a hanging irrigator which can be raised or lowered by pulling a cord up or down. To the long rubber tube of this apparatus, I attached a glass canula of the proper dimension for the size of the blood-vessel of each material, and then I warmed, just before injection, the colour solution to the blootemperature. e) When I obtained the complete injection according to the described manner, I obligated all blood-vessels in the neck; for example, the internal jugular vein, the common carotid artery, etc. and after this injected material had been left in a cold place for twelve hours, I give it the following treatment For the cadaver of man, I cut off the soft parts and the cartilaginous tissues from the bony skull and sawed laterally through the external table according,to the usual technic of section, then I removed the skull-cap leaving the brain and its membranes safe. In this way I got the lower part of the skull-bone containing the petrous bone together with the brain and its membranes. I placed it in the following solution for about one week

8 8 DENJIRO NtABtVA Formalinio parts Hydrochloric acid7 parts Water83 parts, but we must, sometimes, use the following solution for the foetus of man, because the brain of the foetus rarely hardens in such a short time : Formalini o parts Hydrochloric acid7 parts 6o % Alcohol83 parts After about one week it is to be washed in water for 24. hours. This treatment will not perfectly harden and decalcificate it, but what is necessary is only to remove the brain without injury, and to separate easily the petrous bone from the skull, keeping the good colour of the injected stuff by means of this acidity. But with the animal carcases, we need only place each in a 10 % formalin solutionl for one or two days, because their brain and petrous bone are easy to remove and separate from the skull.- f) We must carefully observe the cut ends of the nervus of VII and VIII and their blood-vessels, whether of the brain or of the petrous bone, keeping the dura mater and the arachnoid membrane safe in order to observe the venous and arterial trunks of the labyrinth later on.. After that the stapes must be removed for the benefit of the celloidin, to allow it to penetrate into the labyrinth. When I got a good petrous bone after the above given processes, I passed it through different grades of alcohol, which is accented gradually from 6o %, 70 %, 8o %, 95 % to absolute alcohol, and then a mixture of absolute alcohol and aether, keeping it for 24 hours in each, if it were a human or mammal petrous bone. After this dehydration I placed it in dilute, middle measure, and common concentrate celloidin in succession, for 77-I0 days each, if it were a human bone ; but if it were a mammal, for 1-3 days. After this I dropped it into chloroform and allowed it to hardnn for hours or 2-6 hours according to whether it were a human or a mammal one. Following this, I carefully scraped off the celloidin from the surface of the petrous bone and then placed it in about So % hydrochloric acid for about one week in the case of a human preparation but in the case of animals for 1-3 days.

9 A Study in the comparative Anatomy of the etc. 9 This method was used in order soften the material enough so that with a delicate forceps we might be able to remove the bony tissue in many fragments from the celloidin cast of the cavities in the labyrinth. This preparation was then dehydrated in 95 / alcohol and placed in a small glass dish filled with creosote or a mixture of creosote and isosafurol aa. The latter is more useful than the former, because it ensures the proper hardness of the specimen and deodorizes the creosote. When the specimen became transparent, I carried out the study under the binocular microscope. g) In order to bring to light the delicate points of dispute of previous investigators, I made thick serial sections of 200 mm. horizontal or sagittal direction out of six of the whole number of our cast specimens. These sections we examined under the binocular microscope. We can make such a thick serial preparation by placing a cast transparent specimen again in 96 / alcohol for 24 hours, after which transferring it into concentrate celloidin for 5 hours, and then letting this celloidin containing specimen to harden gradually. The preparation thus completed is carried to the microtome for cutting. To examine the distribution of the blood-vessels on the lamina spiralis and the modiolus, I sliced each coil horizontally u Ider a magnifying-glass with three celloidin cast specimens of the ear of the guinea-pig and two specimens of the human ear. (2) Secondly, I would like to explain in detail the second method which was used on half the number of guinea-pigs, rabbits, and cats used in the study. I transferred their petrous bone after they were injected, and formalinized, as explained already, in the following solution : Hydrochloric acid10 parts 75 % alcohol90 parts In this solution, decalcification of the petrous bone is completed in about three days in the case of the guinea-pig, but in the case of the rabbit and the cat at least two weeks are needed, and during this time the solution must be renewed every day, or every other day. When decalcification was completed, the bony block was washed in water for 12 hours and the membranous labyrinth with a plate of its bone was cut out with a pair of small scissors and a knife from the surrounding tissues under the binocular and dissecting microscopes.

10 I0 DENJIRO NABEYA : This is the most difficult part of the process but with a little care good specimens can readily be made. This was then washed in Distilled waterfor 24 hours and then transferred into 95 % alcoholfor 12 hours and finally submerged in the following mixture Benzol3 parts Isosafuroli part The last step is to extract some air particles that may be in any part of the specimen by placing the preparation in a vacuum. By this treatment, the specimen of the guinea-pig becomes clear and transparent at once, although the rabbit and the cat require from twelve to twenty-four hours more. In this connection we have to note that the benzol used in the solution last mentioned is a volatile liquid and in the course of an examination small quantities of benzol must be added from time to time in ordei to keep the specimen transparent. I also dissected some specimens of this kind in horizontal and sagittal directions by way of a corroborating examination in connection with this subject. A method somewhat different from the above given one which I tried on the dog for a special purpose in connection with this subject, is described in detail in my publication (26). Finally, I shall describe here a method which was similar to this one applied to the human material, thus : A human skull injected according to the above given method was placed in a mixture of formalin and hydrochloric acid for 4-5 weeks renewing the liquid every week. I got an almost completely decalcificated skull, from which I separated the petrous bone. This petrous bone must be placed in the following mixture for about ten days, because a portion of the petrous is particularly harder than other portions of it : Formalin7 parts HydroChloric acid7 parts 70 % alcohol86 parts This mixture should be renewed every day. When I obtained complete decalcification in this way, I washed the bone in water for 24 hours. Then I cut off sections about two millimeters each thick, laterally or longitudinally to the axis of the modiolus. After that I

11 A Study in the Comparative Anatomy of the etc. II bleached it in the following mixture for hours : Peroxide hydrogen4 parts 95 % alcohol7 parts Bleaching should be perfectly carried out, for if it be imperfect the specimen would not be successful. Finally, it is submerged in creosote or a mixture of isosafurol and benzol for six hours after dehydrating it in absolute alcohol. This method was used in one of the monkey and ten cases of man. * * For the differential judgment of the arteries and veins, I may state the general principle, namely, the arteries present a markedly tortuous course, while the veins are on the whole smooth and less curved. The capillaries must also be distinguished as to whether they branch out from the arteries or from the veins. The best way to describe the arterial and the venous systems in any given specimen is to make a series of drawings under the binocular microscope, using occasionally the sign apparatus-der zeichen Apparat (25 P. 1356). Sometimes it may be necessary to repeat the drawings many times in order fully to comprehend the complete system. For tnis purpose the use of the binocular microscope is essential ; but the research into the capillaries may sometimes be made to advantage by using the general compound microscope. The course of the capillaries as well as their connections are best seen when we follow them under a general compound microscope constantly by changing the focus as the eye pursues their varied courses. To finish this chapter, I must suggest an important matter relating to the corroboration of the origins of A. auditiva interna and Vv. auditivae internae on the basal brain. It is to be regretted that, although Siebenmann studied this artery with some human materials and one monkey, using the injection according to Teichmann's method, he did not do it completely. I examined all my materials, taking out safely the brains from the skull according to the above given methods, making transparent specimens of the basal brain which was separated from the skull together with the arachnoid and the pia mater and submerged in creosote. This examination, moreover, was supplemented by 48 human brains prepared by other hands, using Teichmann's method, in the dissecting room of this Imperial University of Kyoto.

12 12 DENJIRO NABEYA I must add that while engaged in this study I also made a referring study of the cut ends of the blood-vessels and of the nerves on the side of the petrous bone and on the side of the brain, to ascertain their running conditions by many more than fifteen human materials in practical dissections. At any rate, the study of this portion was by no means simple, and closest attention and meticulous accuracy were essential. Materials for this research. I used the following materials in this study : I) Rodentia94 rabbits (Lepus Cuniculus)17 2) Carnivora32 3) Primates2 guinea-pigs (Cavia Cobaya)67 rats (Epimys Norvegicus var. Albus) Ic dogs (Canis Familiaris)23 cats (Fells Domestica)9 monkeys (Macacus Fuscatus)2 4) Homo (Japonicus) 24 adults8 fetus16 Total(ears 304)152 Supplement ; the reference to the origin of the arterial trunk in the labyrinth is as follows : Human brains48 which had colouring-matter already injected into the blood vessels in the dissecting-room of the anatomical department of the Imperial University of Kyoto.

13 A Study in the Comparative Anatomy of the etc. 13 I. Guinea-pig (Cavia Cobaya). Observation of 134 ears and 67 skulls This is the results of the above number of perfect injected materials which have undergone closest scrutiny. I think that the guinea-pig is the best material for the investigation of the bloodvessels in the labyrinth, and hence, study of it makes a fine preliminary step toward studying other materials. When we understand the blood-vascularization of the guinea-pig, it will be easy for us to understand it in other animals. Arteries. A. labyrinthica of the guinea-pig. According to my careful examination, it is not an independent artery which arises directly from A. basilaris, but a branch of A. cerebelli inferior anterior which corresponds to that of the human skull. This is, however, the common trunk of three main branches, namely, A. vestibuli anterior, A. vestibuli posterior, and A. cochleae propria in the labyrinth ; these branches ramify in the following order : After the first main branch, A. vestibuli anterior, is given off at the outside of the porus acusticus interrus from the common trunk, a sub-trunk which is called A. cochleae communis remains in the meatus acusticus internus, but it divides itself into two main branches, namely, A. vestibuli posterior and A. cochleae propria at the base of the modiolus. I found, however, sometimes a variation in which A. vestibuli anterior and A. cochleae communis each arise directly from A. cerebelli inferior anterior without the common trunk. (I) A. vestibuli anterior (Pl. I. ava). It comes into the anterior district of the vestibule along the R. anterior of N. acusticus (Utriculoampullar nerve) after separating from the trunk. Its course describes many minute spirals, and on its way it gives off many branches in the meatus acusticus internus and the labyrinth. Leaving the branches in the meatus acusticus internus, let us now proceed to the next point : The first branch of this artery in the labyrinth is the finest twig which is distributed to the fore margin of the saccule and the utricule ; and the second branch is A. utricularis which is distributed to the

14 14 DENJIRO NABEYA macula acustica utriculi. After a while the trunk of this artery divides into two terminal branches, one of which is A. ampullosemicircularis lateralis, and the other A. arnpullo-semicircularis anterior. The former is distributed to the crista ampullaris lateralis by giving off a few twigs, and runs over the semicircular canal in the form of one or two elongated branches, the latter supplies the crista ampullaris anterior by giving off some twigs, and goes to the semicircular canal along the inner side of its ampulla and its canal, parallel with one fine elongated branch which emerges from the anterior portion of its ampulla and runs over the semicircular canal. Many fine twigs are, moreover, given off from the trunk of this artery to its nerve as well as to N. facialis in the meatus acusticus internus. (2) A. vestibuli posterior (avp, in Pl. I, IV, V, VI). It is divided from A. cochleae communis (Pl. acc) at the lower point of the basal coil just outside N. cochlearis, leaving A. cochleae propria, and takes an oblique course postero-inferiorly along the inner margin of the descending portion of the basal coil, and divides into two branches, one of them is a small one which is the branch of the vestibular blind sac, and the other is a large one which supplies the crus commune and the emus simplex lateralis and the arnpullo-semicircularis posterior after crossing V. vestibuli posterior. Before it divides into the abovementioned two branches, it has, however, other branches, one of which supplies the macula acustica sacculi, the so-called A. saccularis (as. in Pl. I. IV.), the other being some small twigs which are distributed to the spiral ganglion and the basal portion of the modiolus (gs. in Pl. III. IV. V. VII). In addition to the above, moreover, I must note, especially, some elongated capillaries, namely, one running over the wall of the scala vestibuli and another over the wall of the fenestra cochleae and the canaliculi cochleae (dotted line in Pl. I). a) The small branch, i. e. the vestibular blind branch, runs along the inferior margin of the basal coil which is holding the blind sac, and corresponding to the antero-inferior margin of the scala vestibuli, at first descending from posterior to inferior, and then ascending antero-laterally. This branch sends off some small and short twigs to the proximal portion of the stria vascularis and the ligamentum spirale on the lower part of the basal winding. Some other small twigs, moreover, run over the vestibular blind sac (vbb. in Pl. I. V.). The branch ends in anastomosing with the terminations

15 A Study in the Comparative Anatomy of the etc. 15 of the first primary branch of A. cochleae propria (s. sub. 3) on the lower third of the descending basal coil. b) The large branch is the continuous portion of the trunk of A. vestibuli posterior. It gives off R. cruris communis at first shortly after its breaking off from the former, namely, the vestibular blind branch ; and then before long it divides into two terminal branches, one of which is R. cruris simplex lateralis and the other is A. ampullosemicircularis posterior. R. cruris communis goes down to the end of the crus commune, passing the dorsal surface of the vestibule and giving off some small branches on a portion of the sinus superior of the crus commune. When this ramus reaches a portion of the crus commune, it curves from behind to the front clinging to the endosteum for a short distance and then going back to the anterior surface of the membranous crus commune, finally dividing into two terminal branches, one to the crus of the posterior semicircular canal, and the other to the crus of the anterior semicircular canal. These two terminal branches anastomose with the terminations of other arteries and veins which come from the opposite crura respectively. R. cruris simplicis lateralis goes down to the summit of, the crus simplex laterale along the concave side of its crus, giving off some capillary branches there, finally its terminal branches anastomose with the fellow branches of the opposite ramus as the former does. R. ampullo--semicircularis posterior goes down to the ampulla posterior and its crus. On the way it gives off a small branch which is called A. nervi ampullae posterioris by ASAI in his dog's ear, -with some other smaller branches which supply the crista ampullaris posterior and its vicinity. Both the latter, namely, the rami of the ampullo semicircularis posterior and of the crus simplex lateralis accompanied, in general, each fine parallel branch on the posterior canal and on the crus simplex, Just as in the case of A. vestibuli anterior. A. vestibuli posterior has no R. cochleae which is decribed by AsAI, as a very pawerful branch sending off many twigs to the vestibular portion of the basal coil, in ears of his dog and rat. (3) A. cochleae propria. This is the continuous portion of the original trunk, namely, A. labyrinthica and A. cochleae communis, for it is known by its name after it gives off A. vestibuli posterior on the lateral side of the nervus cochlearis at base of the first coil.

16 16 IJ EN J-I RO NABEYA : ---- It arises, therefore, at the point of division of A. vestibuli posterior, and ascends to the top coil along the wall of the modiolus, which corresponds, perhaps, to the tractus arteriosus spiralis foraminulentus of man, taking a spiral course ; that is to say, starting from the middle outside of the base of the modiolus, it first goes obliquely to the superior and posterior side and thence to the anterior and exterior outside, this alternate direction being repeated as many times as there are coils, it finally reaches the top of the modiolus, where it, breaks up into three or four terminal branches on the inner side of the blind sac. Upon counting the number of these primary branches, namely, at the roots of the radiating arteries,. I obtained the figures 10--I i in the entire cochlea, distributed as follows : four branches in the first coil, two or three in the second, and three or four in the third and other coils. I also counted the number of the radiating arteries on the surface of the scala vestibuli of the entire cochlea, and found it to be 6o-8). When I counted the exact number of the coils of the cochlea and the radiating arteries on each coil of a guinea-pig I found the following : The method of counting I used was the following : I drew a straight line from the frontal margin of the fenestra cochleae to the opposite side through the top end of the blind sac. Each radiating artery which appears on the spiral zone of the summit of the scala vestibuli was counted as one trunk although it might branch off at the lower end. Note the following illustration : Although I was not able to make an exact count of all the radiating arteries on the lamina spiralis, the number of the arteries counted on the basal coil alone was about 45 ; hence it may be inferred that the total number is greater than that of the scala vestibuli. I must not neglect to mention the first primary. branch of A. cochleae propria which is the longest branch given off by this artery (fpb. in Pl. I. IV. V.). It arises from the lowest portion of the trunk of this artery and runs along the margin of the wall of the scala

17 A Study in the Comparative Anatomy of the etc. 17 Fig. I. vestibuli and goes down posteriorly ; its terminal twigs anastomose with the endings of the vestibular blind branch of A. vestibuli posterior. Other primary branches of the series of radiating arteries of the scala vestibuli arise from A. cochleae propria all along its whole length. The radiating arteries of the scala vestibuli are terminal branches of the above primary branches and arch over the wall of the scala vestibuli resembling a open Japanese umbrella in appearance. One further series of radiating branches must be noted, namely, those which supply the lamina spiralis. They arise both directly from the main trunk of Al cochleae propria, and indirectly from the primary branches of the radiating arteries of the scala vestibuli. They form two spiral vessels and one spiral zone of the capillary network with

18 18 DENTJIRO NABEVA : capillaries of the companion veins along the peripheral zones of the lamina spiralis. These two series of radiating arteries are distributed,. one accompanying the other, on the same coil, agreeing with the observations of Siebenmann in the human ear, and of As.li in his dog's and rat's ears, and of the ears of all my other subjects. I failed, however, to find an example of the interesting variation which was found by Shambaugh in the ears of his pigs, i. e., the radiating arteries of the lamina spiralis of one coil supplying the similar structure of the coil next above. Every one of those arterial branches, namely, the primary branches from the trunk of this artery, the radiating arteries of the scala vestibuli and the radiating arteries of the lamina spiralis describe numerous minute spirals on their fine trunks. These condition are designated " Die Glomerli arteriori der Gehorschnecke " by SCHWALBE (12, 13) ;. but the branches are never seen to form loops due to anastomosis among themselves, as in the cases of the pig and the calf of Shambaugh, or the so-called " arcade " of the human ears of Siebemann, which in the ears of my human material was seen to be of very variable number. individually, while among my mammals I came across only one or two arcades. A. cochleae propria has further a series of fine twigs which supply the ganglion spirale and many small twigs which supply the modiolus. These two arise both directly from the trunk of this artery, and, indirectly, from the primary branches. Veins. Hopmann published his study of the blood-vessels in the labyrinth of the guinea-pig and he says, " The guinea-pig has only a venous trunk " (5). It is certain it has one venous trunk, but it is not so simple as he sweepingly states, because I came upon a network of complicated blood-vessels on the sheaths of the nervus acusticus, namely, the dura mater, the arachnoid and the pia mater, and the nervus itself, and in addition one trunk which resembles a central vein of the Vv. auditivae.internae. This fact is liable to lead us into a misunderstanding similar to the descriptions of Siebenmann (man), and of AsAI (the dog and the rat) ; but if we were to examine the conditions painstakingly, we should obtain sure and certain knowledge

19 A Study in the comparative Anatomy of the etc. 19 that it has not a systematic connection with the venous system of the labyrinth. I got the clear impression thru all my exact observations that it belonged to the dura mater or the arachnoid in the meatus acusticus internus, and I never found a venous trunk which penetrated into the nervus axis and connected with the venous trunk of the membranous labyrinth at the base of the modiolus. I must add that sometimes I found a developed system of the V. aquaeductus vestibuli, while sometimes there was but a trace of it. I propose to classify the veins of the membranous labyrinth of the guinea pig in order simply to explain this complex system : Table I. The venous system of the membranous labyrinth of the Guinea-pig. V. Canaliculi Cochleae a) V. spiralis posterior Vv. radiatae scalae tympani primae Vv. radiatae laminae spirales primae Vv. ganglionum spiralium b) V. fenestrae cochleae Vv. radiatae scalae tympani secundae c) V. vestibuli posterior Vv. radiatae laminae spirales secundae I. V. saccularis 2. V. vestibuli anterior lateralis V. saccularis inferior V. utricularis V. ampullo-semicircularis anterior V. ampullo-semicircularis lateralis 3. V. cruris communis 4. V. ampullo-semicircularis posterior et cruris simplicis V. cruris simplicis R. ampullaris posterior V. ampullo-semicircularis posterior Vv. auditivae internae These are veins accessory to this venous system limited to the meatus acusticus internus. I shall describe the vein in detail:

20 20 DtNJIRO NABE7A V. canaliculi cochleae, which, passing through the aquaeductus cochleae, receives all the venous blood of the membranous labyrinth in the guinea-pig. The venous system of this labyrinth, however, is deficient in two veins, i. e., V. spiralis anterior, and V. vestibuli anterior which are seen in the ears of other mammals. a) V. spiralis posterior. The course of this vein begins at two points of the, top coil with the capillary veins, i. e., the termination of the lamina spiralis and the outer walls of the blind sac, and of the scala vestibuli, and goes down to the, basal coil along the internal margin of the scala tympani, describing a spiral course. When it reaches the beginning of the descending basal winding, its direction changes posteriorly and joins the V. canaliculi cochleae. On its way it receives three series of the branches : The first are Vv. radiata scalae tympani primae beginning from the ligamentum spirale, the stria vascularis, and sometimes from the wall of the scala vestibuli, each combination of veins, growing in a row on the scala tympani. I counted the number of the combinations of this series, and the number was 28-40, excepting, of course, the Vv. radiatae scalae tympani secundae which belong to V. fenestrae cochleae (vsp, vfc, in Pl. II, IV). The second consists of Vv. radiatae laminae spiralis primae which begin from the spiral vessels and the capillary zone of the edge of the lamina spiralis and run over the upper and lower surfaces of the lamina spiralis toward the modiolus. They gradually come together each into a combined branch as does the former, and empty into the trunk of the mother vein along the inferior and internal portion of the lamina spiralis. The number of these veins is 15-2o at their stems, ' excepting the Vv. radiatae laminae spiralis secundae; The third are a series of small twigs i. e., Vv. ganglionum spiralium, coming from the spiral ganglion. These twigs are very fine and connect directly with the trunk of V. spiralis posterior, or indirectly with the stems of, two sets of the radiating veins above mentioned. b) V. fenestrae cochleae. It is a single long vein which starts at the anterior margin of the vestibular blind sac, ascends along the margin of the fenestra cochleae, then runs down the posterior, and when it reaches the inferior portion of the basal winding, connects with the head of V. canaliculi cochleae, together with V. vestibuli posterior. In its course it receives many short twigs, such as Vv. radiatae scalae vestibuli secundae which begin at the ligamentum

21 A Study in the Comparative Anatomy of the etc. 21 spirale and the stria vascularis, and then empties into this vein, together with the stems _ of a number of the capillary groups (vfc, in Pl. II, IV, V). c) V. vestibuli posterior. It collects all the vestibular venous branches as illustrated in Table I. I shall describe the veins in the order given in the table here referred to. Vv. radiatae laminae spiralis secundae. Two or three radiating veins of the lamina spiralis on the vestibular portion of the basal winding connect with V. vestibuli posterior as illustrated in Plates II., V. vrs. I have not seen any mention by previous investigators of the existence of these veins in the human ear and in the ears of mammals. These branches too receive some twigs of the ganglion spirale and of the modiolus. ~. V. saccularis. It is a vein in the macula acustica sacculi. Hence, the capillary of the twigs begins from the capillary network formed by the arteries in the macula acustica sacculi and runs posteriorly along its inferior margin, to connect finally with the middle portion of V. vestibuli posterior (vs. in P1. II. IV). 2. V. vestibuli anterior lateralis. This is the general term. applied to a group of four veins, namely : V. saccularis inferior which is a thin vein running along the inferior margin of the saccule to connect with the trunk ; V. utricularis which begins at the anterior surface of the utricle, running on the dorsal surface of the utricle to connect with the trunk ; V. ampullo-semicircularis anterior which comes from the anterior semicircular canal and its ampulla to connect with the trunk ; V. ampullo-semicircularis lateralis which takes a similar course as the former but on the lateral canal (vval. in Pl. II. VI). 3. V. cruris communis, It commences in two separate branches, each of which begins of the summits of the anterior and the posterior semicircular canals and running along their membranous surfaces toward the crus commune, finally unites with the other at the lower portion of the crus commune. This vein, thence, goes to the vestibule taking a somewhat spiral course aldng the membranous crus commune and for a short distance clings to the periosteum and finally unites with V. vestibuli posterior. 4. V. ampullo-semicircularis posterior et cruris simplicis lateralis is a vein which gathers up the following branches :

22 22 EFNJIRO NABEYA V. cruris simplicis which beginning from the summit of the semicircularis lateralis and unites at the inferior portion of the vestibular blind sac with R. ampullaris posterior ; R. ampullaris posterior which comes from the neighborhood of the sulcus ampullaris and joins with the former branch. This ramus corresponds with A. nervi ampullaris posterior on the opposite side. V. ampullo-semicircularis posterior runs on the structure after which it is named, and unites with the stem of the first branch abovementioned at a higher level, and finally empties into V. vestibuli posterior at its proximal end (vasp. in Pl. II, IV, V, VI). To close this paragraph, I must add that each V. ampullo-semicircularis arches over the back dome of the membranous ampulle, just as Shambaugh describes for his sheep, or as Siebenmann for his human ear, but it is not embedded in the endosteum. Vv. auditivae internae. They consist of some veins of the meatus acusticus internus as follows ; V. nervi acustici. It collects a part of the venous blood from the sheath of N. acusticus, which circulates from the N. acusticus itself, penetrates into the petrous bone and finally connects with a vein in the bony substance as well as with V. canaliculi cochleae (vna. in Pl. II, V, VI). The termination of this vein anastotnoses always with the root of the plexus auditivae internae at an anterior portion of the porus acusticus internus. Plexus auditivae internae. I can see, moreover, innumerable capillaries on the sheath of N. acusticus, and on the nervus itself in the meatus acusticus internus, and also the venous network which is formed by the venous roots of those capillaries. In this plexus, I found a fine venous trunk which emerges from the fundus of the meatus acusticus internus and runs down on the dura mater or the arachnoid and connects with the venous network abovementioned. I shall call it " V. auditiva intern a" but this vein neither penetrates into N. acusticus itself, nor connectis directly with the blood-vascular system in the labyrinth. The Capillary Areas. The capillary areas are the most important portion of the bloodvascular system of the membranous labyrinth because of their very delicate functions. They are, therefore, very difficult graphically ta

23 A Study in the Comparative Anatomy of the etc.23 work out, especially is such the case with the fine and dense structure found in the guinea-pig. The following results have been obtained in my researches : (I) The top coil. The vascular system in the top end of the lamina spiraiis is composed of two kinds of capillaries, one arterial capillary which comes down, breaking out from the root of the terminal branch of A. cochleae propria along the helicotrewa, i. e., the inner margin of the lamina spiralis, and one venous capillary which is the terminal twig of Vv. radiatae laminae spirales primae. There are also some arterial capillaries of A. cochleae propria, namely, the radiating arteries of the lamina spiralis in the top coil, and some venous capillaries of Vv. radiatae laminae spirales primae in the same coil. These capillaries consist of certain anastomotic loops which are the beginning portion of each spiral vessel of the lamina spiralis formed by the connection with each other on the edge of the lamina spiralis. The wall of the blind sac which is the end portion of the top coil is provided with an irregular network formed by the very fine capillaries of the terminal twigs of A. cochleae propria and of V. spiralis posterior, anastomosing with the network of some capillaries in the stria vascularis and the ligamentum spirale. The blood-vascular syatem of the stria vascularis a.nd the ligamentum spirale begins in the neighborhood of this sac (2) The ganglion spirale. I can see that this area possesses a characteristic capillary arrangement along the outer wall of the modiolus and at the root of the lamina spiralis. The arteries here are small serial twigs of A. cochleae propria, that are given off directly from the trunk, or indirectly from its branches. But the proximal portion of the basal coil is supplied by the twigs from A. vestibuli posterior. The veins on this area are small twigs which empty into the V. spiralis posterior. Some capillaries on the ganglion at the base of the cochlea, sometimes connect with some capillaries of V. auditiva interim and the venous capillaries of the modiolus itself. The vessels on the ganglion appear mostly to supply then sheath of the ganglion, but when examined the cut surface of the ganglion which had been exposed to view by cutting the cochlea horizontally, i. e., in the plain perpendicular

24 24 DENJIRO NABEYA : to the long axis of the modiolus, I also found some very fine capillaries supplying the substance of the ganglion, the vessels running into the mass of the nerve cells (gs in Pl. V, VII). (3) The lamina spiralis. At first attention is directed to the spiral vessels on the peripheral margin of the lamina spiralis arranged in two sets on the basilar membrane and the crista spiralis : One set which is on the basilar membrane, is the lower and is composed of two rows of the spiral vessels in each coil, excepting at the proximal end of the basal coil where they are somewhat irregular. They are formed by the continuation of the anastomotic loops of the radiating vessels. The first few run under the tunnel of Corti's organ forming very marked wide anastomotic loops of the radiating vessels on the lamina spiralis. The second row runs along the labium tympanicum formed by the continuation or intermittence of many anastomotic loops of the radiating vessels on the lamina spiralis. The former is called outer spiral vessel, the latter the inner spiral vessel by other investigators. w The other set which is on the crista spiralis, is the upper and forms one spiral zone of the capillary network of large and irregular mesh on the crista spiralis ; in other words, between the outer edge of the crista spiralis and the stuck line of the membrana Reissneri. I could not recognize this zone as two rows of spiral vessels on the crista spiralis, as described by VOLTOLINI (23), SCFIVALBE (I4), etc. I must also state that the ear of the guinea-pig has not the V. lamina spiralis, called " die Spiralblattvene " by Siehenmann. This vein is formed by the anastomotic continuation of the root portion of the radiating veins of the lamina spiralis, running along the zone of the root portion of the lamina spiralis. I saw radiating branches side by side on the lamina spiralis each of which is a combination of some, or of many, radiating veins uniting at the root. A specially big combined branch exists on the lamina spiralis of the descending portion of the basal coil (PI, II, V, VII). At any rate, the beginnings of these spiral vessels are the radiating arteries of A. cochleae propria and Vv. radiatae laminae spirales primae of V. spiralis anterior. However,, some radiating veins on the proximal portion of the lamina spiralis, which lies the descending portion of the basal winding, belong to V. vestibuli posterior, i. e., Vv. radiatae laminae spirales secundae, and some

25 A Study in the Comparative Anatomg of the etc. 25 radiating arteries belong to V. vestibuli posterior as already mentioned. We can, moreover, see the anastornosis of the capillary vessels here and there s on the bony portion, namely, its periosteum and its containing nerves, of the lamina spiralis (sp. szc. in P1. III. VII.) I have never seen any blood-vessels on the membrana Reissneri and the zona pectinata. (4) The ligamentum spirale and the stria vascularis are supplied by the peripheries of the radiating arteries of the scala vestibuli and Vv. radiate scalae tympani primae, but their proximal portion, namely, in the descending portion of the basal winding, are supplied by the twigs of the branch of the vestibular blind sac and V. fenestrae cochleae (vbb. vfc. in P1, V). The capillary network of the stria vascularis is built by the occasional branches of these vessels. These capillaries appear to possess a certain degree of laxity and pursue a more serpentine course than those on the ligamentum spirale. The network on the liga mentum spirale is supplied by the terminal arteries of the radiating arteries and also by the innumerable terminal veins of Vv. radiatae scalae tympani primae and secundae, as mentioned above. They form two parallel spiral vessels, one passing through the crista basilaris, the other through the prominentia spiralis. There are other capillaries built into a dense network in the ligamentum spirale, but their relation with those of the stria vascularis is that of one placed on top of the other along the upper and lower portions of the prominentia spiralis except at the lower half of the basal winding. See figure 2. These relative positions differ from those in the human ear and those, of other mammals, except perhaps the rat of AsAJ. But at the same time the elongated terminal veins ascend the wall of the scala vestibuli over the ligament= spirale and anastomose with the fine branches of the radiating arteries. I also found some elongated capillary arteries on the area surrounding the fenestra cochleae, two of which arise from the root of A. vestibuli posterior, and run through the scala tympani to reach the margin of the fenestra cochleae (ep, es. in Pl. IV), and another arises from a point near the former of the same trunk, but ascends the wall of the scala vestibuli to supply the superior portion of the fenestra cochleae (et in P1. IV). (5) The vestibular blind sac and the ductus perilymphaticus. The vestibular blind sac signifies anatomically the proximal portion of the basal coil, and its vascularization is irregular. Its arterial supply