On the Muscles of the Gluteal Region of the

Transcription

1 On the Muscles of the Gluteal Region of the Macacus cyclopsis By Masatada Sugiyama First Department of Anatomy, Faculty of Medicine, Nagasaki University (Director : Prof. Dr. Jun-ichiro Satoh) A good number of studies have been reported on the muscular system of primates, but excluding a few the majority of these reports are on comparative anatomical studies using a small number of cases. It is, therefore, dangerous to attempt an assumption of the normal standard condition of a certain species of animal directly from these findings. In order to ascertain the normal condition of a certain type of animal it is necessary to decrease the error associated with individual differences by studying a large number of cases of one type of animal. Based on this viewpoint detailed statistical studies on various organ systems of the Macacus cyclopsis are being conducted by this Department using the large number of cases collected by Professor Satoh in an effort to grasp the normal condition of the Macacus cyclopsis. This author participating in this endeavor conducted a study on the muscles of the gluteal region. Research Method and Material Of the Macacus cyclopsis cadavers fixed in 10% formalin solution and kept in this Department, a total of 25 cadavers, 15 male and 10 female, were used as material, upon which observations were conducted on gluteal muscles of both sides. Gross anatomical observations were made on the individual muscles and, when deemed necessary, a magnifying lens was used. Special care was exercised with reference to nerve supply and, moreover, care was not neglected on the relationship with the blood vessels. 1

2 2 Masatada Sugiyama Findings and Consideration A. General finding of the muscles of the gluteal region The muscles of the gluteal region are enveloped by the Fascia glutea which is continuous with the Fascia thoracolumbalis above. The central portion of this fascia is attached by strong fibers to the upper and outer margins of the Tuber ischiadicum. The fascia runs downward toward the flexor and lateral sides of the thigh to continue with the Fascia lata. The gluteal muscles can be classified into three parts according to their relative positions that is, the muscles located in the superficial layer, that in the deep area, and the muscles between these two. The muscles that constitute the first layer are called the M. gluteus superficialis in mammals and as made up of M. gluteus maximus and M. tensor fasciae latae. The M. gluteus maximus, excluding the fasciculi occupying the medial side, is a comparatively thin muscle, occupying the major part of the posterior surface of the gluteal region. The lower part is covered by the flexor muscles of the thigh and is inserted into the femur, while the lower lateral part is united with the M. tensor fasciae latae. The M. tensor fasciae latae, located on the lateral side of the gluteal region, is adhered to the anterior margin of the M. gluteus maximus and ends at the Tractus iliotibialis. The second layer is made up by the M. gluteus medius and M. piriformis. The M. gluteus medius covered by the M. gluteus maximus is a large strong muscle occupying the central part of the gluteal region and inserts into the upper half of the Trochanter major. The large part of the M. piriformis is covered by the M. gluteus medius, but only a part of the medial side directly adjoins the ventral surface of the M. gluteus maximus. Moreover, the part below the central part of its venter is firmly united with the ventral surface of the M. gluteus medius and is inserted into the tip of the Trochanter major. In the third layer are located the M. gluteus minimus and the short pubo-ischiofemoral muscles. The posterior side of M. gluteus minimus is covered by the M. gluteus medius 5 while its lateral side is covered by the M. tensor fasciae latae. The short pubo-ischiofemoral muscles are made up of M. gemellus, M. obturatorius internus, and M. quadratus femoris and occupies the region between the Tuber

3 On the Muscles of the Gluteal Region of the Macacus cyclopsis 3 ischiadicum and the hip joint. A part of its side of insertion is covered by the posterior margin of the M. gluteus maximus. B. General findings of the nerve supply of the gluteal muscles The N. piriformis, N. gluteus superior, N. gluteus inferior, and N. pubo-ischiofemoralis are the nerves which are distributed to the gluteal muscles. These nerves emerge from the Foramen ischiadicum majus, together with the N. ischiadicus which emerges from the Foramen ischiadicum majus and runs down the central part of the ventral surface of the M. piriformis and the posterior surfaces of the M. gemellus and M. quadratus femoris to the thigh. The N. gluteus superior runs along the posterior lateral side of the N. ischiadicus and passes through the Foramen suprapiriforme to emerge at the outer fringe of the Incisura ischiadica major where it branches out in radial fashion. The N. gluteus superior was calssified into the following three groups. The first is the Ramus superior which emerges at the upper lateral margin of the Foramen ischiadicum majus and supplies the M. gluteus medius. The second is the Ramus lateralis which emerges at the central part of the lateral margin of the Foramen and supplies the M. gluteus medius, M. gluteus minimus, M. tensor fasciae latae, and M. gluteus maximus. The third is the Ramus inferior which emerges at the inferior lateral margin of the Foramen ischiadicum majus and descends along the medial margin of the M. gluteus minimus to supply the M. gluteus minimus. The N. gluteus inferior and N. piriformis overlap at the posterior surface of the N. ischiadicus and emerge from the Foramen infrapiriforme. The N. gluteus inferior descends along the ventral surface of the M. piriformis is reflected lateralward at the inner margin of the M. gluteus medius and supplies the M. gluteus maximus from veneral. The N. piriformis upon leaving the Foramen ischiadicum majus immediately branches into two and enters the M. piriformis from the ventral surface. In addition, the N. cutaneous femoris posterior runs together with these two nerves, but it is a cutaneous branch which is not directly associated with the gluteal muscle. The N. pubo-isclaiofemoralis descends along the ventral surface of the N. ischiadicus and the medial margin of the M. gluteus minimus, and divides into two branches, Ramus medians and Ramus

4 4 Masatada Sugiyama lateralis, to supply the M. gemellus and M. quadratus femoris. C. Findings and consideration on various muscles (Figs. 1, 2, 3, 4). 1. M. gluteus maximus As in the case of other primates, the development of the M. gluteus maximus is poor in comparison with that of man. Origin ; The origin is made up of three parts ; the gluteal aponeurosis which arises tendinously from the entire crista iliaca, the strong muscular origin which is from the coccygeal vertebra, and the small muscular origin between these two which arises from the Fig. 1. Muscles of the gluteal region (superficial layer) 1) M. gluteus maximus 10) M. biceps femoris 2) M. tensor fasciae latae 11) M. semitendinosus 9) M. obliquus abdominis externus 12) M. semimembranosus proprius *) Tractus

5 On the Muscles of the Gluteal Region of the Macacus cyclopsis 5 dorsal fascia located on the posterior surface of the sacrum. i) Origin from the coccygeal vertebra The ventral surface of the origin is muscular, while the posterior surface is aponeurotic. In most of the cases (76%) the origin is from the transverse process of the first coccygeal vertebra, but there is a considerable number (24%) in which it arises not only from the transverse process of the first cocygeal vertebra but also that of the second coccygeal vertebra. (Table 1) These fasciculi arising from the coccygeal vertebra are thicker and stronger, being about three times thicker than that arising Fig. 2. Muscles of the gluteal region (second layer) 1) M. gluteus maximus 9) M. obliquus abdominis externus 2) M. tensor fasciae latae 10) M. biceps femoris 3) M. gluteus medius 11) M. semitendinosus 6) M. gemellus 12) M. semimembranosus proprius 7) M. obturatorius internus 13) M. vastus lateralis 8) M. quadratus femoris 14) M. ischiocaudalis

6 6 Masatada Sugiyama from other parts. Among those arising from the coccygeal vertebra, not one case of a so-called M. caudofemoralis in which there is a complete separation and independence was found, but separation only on the ventral surface suggestive of M. caudofemoralis was noted on both sides of one body (4%). ii) Fasciculi with tendinous origin Aponeurosis which arise from the entire crista iliaca are thin but strong and especially the fibers arising from the spina iliaca anterior superior and spina iliaca posterior superior are strong and spread out in radial fashion. The anterior margin of the tendinous fasciculi of origin covers and adheres with the M. tensor fasciae Fig. 3. Muscles of the gluteal region (deep layer) 1) M. gluteus maximus 7) M. obturatorius internus 2) M. tensor fasciae latae 8) M. quadratus femoris 3) M. gluteus medius 10) M. biceps femoris 4) M. piriformis 11) M. semitendinosus 5) M. gluteus minimus 12) M. semimembranosus proprius 6) M. gemellus 13) M. vastus lateralis

7 On the Muscles of the Gluteal Region of the Macacus cyclopsis 7 Fig. 4. Nerves supply of the gluteal museles 3) M. gluteus medius 8) M. quadratus femoris 4) M. piriformis 13) M. vastus lateralis 5) M. gluteus minimus 14) M. ischiocaudalis 6) M. gemellus 15) M. obturatorius externus 7) M. obturatorius internus latae, but the degree of adhesion varies to a considerable extent. Adhesion is always marked at the inferior part. Moreover, there

8 8 Masatada Sugiyama Table 1. Origin from the coccygeal vertebra was one case each in which the anterior marginal fasciculus of these fasciculi separated or the ventral fasciculus at the anterior margin separated to be adhered with the posterior surface of the M. tensor fasciae latae. Insertion : The muscle is either inserted into the femur or is continuous with the tractus iliotibialis. i) Insertion into the femur The muscle fibers of the fasciculi arising from the coccygeal vertebra run down almost parallel and are inserted into the femur. The posterior margin of the muscle generally runs down at some distance from the Tuber ischiadicum, is covered at the lower part by the origin of the M. biceps femoris but without adhesion to this muscle, and attaches muscularly to the Tuberositas glutea located at the inferior posterior part of the Trochanter minor. One localized part attaches aponeurotically. In the course of insertion, it enters between the flexor muscles and extensor muscles of the thigh as the continuation of Tractus iliotibialis accompanied by Septum intermusculare laterale and separates these two groups. There was only one case (2%) in which the inferior margin of this muscle and the Tuber ischiadicum almost adjoin each other. The Loth index which compares the distance from the head of the femur to the distal point of the insertion and the length of the femur (the length of the femur is the distance from the knee joint line to the head of the femur) was 60 or less in 4%, 70 or less in 20%, 80 or less in 58% and 90 or less in 18%, but in no case did it drop below the center of the femur. ii) Insertion into the Tractus iliotibialis

9 On the Muscles of the Gluteal Region of the Macacus cyclopsis 9 Among the tendinous bands of origin and the muscular bands of origin, the anterior margin of the remaining part excluding the aforementioned coccygeal vertebra origin covers and adheres to the posterior margin of the M. tensor fasciae latae, but the adhesion at the lower part is very firm and can be more properly expressed as being a union. At the upper one third of lateral side of the thigh it is continuous with the Tractus iliotibialis, but the point of continuation is located below the site of insertion of this muscle into the femur, midway between the site of insertion of the M. tensor fasciae latae. Relationship with the surrounding muscles The M. tensor fasciae latae is most closely related to the M. gluteus maximus and in all cases the lower lateral margin of the M. gluteus maximus covers the posterior margin of the M. tensor fasciae latae with some adhesion at the upper part and firm union at the lower part. The degree of adhesion and union is varied, but in the greatest number of cases (44%) there was adhesion extending throughout the length of the muscle. As mentioned earlier, there were two cases in which the fasciculus separated from the M. gluteus maximus united with the posterior surface of the M. tensor fasciae latae. In all cases the aponeurosis of origin is adhered to the posterior surface of the M. gluteus medius, but no adhesion with the M. gluteus minimus was noted. Nerve supply This muscle is supplied almost completely (98%) by the N. gluteus inferior and the N. gluteus superior. i) N. gluteus inferior This is an independent branch which emerges at the foramen ischiadicum majus on the lateral posterior surface of the N. ischiadicum, reflects at the medial margin of the M. gluteus medius and runs downward and lateralward to divide into two branches that distribute to the M. gluteus maximus. It appears as if these two branches are separately distributed to the fasciculi arising from the coccygeal vertebra and the tendinous fasciculi of origin of the M. gluteus maximus, but no definite separation of innervation could be demonstrated.

10 10 Masatada Sugiyama As for abnormal cases, we noted 4% in which the course of this nerve is imbedded within the N. ischiadicus for a longer distance with separation at a slightly more distal part and 2% in which small branches are sent to the M. piriformis. ii) N. gluteus superior The small branch from the R. lateralis of the N. gluteus superior is distributed to a part of the anterior margin of the M. gluteus maximus. At the central part of the lateral margin of the Incisura ischiadica major, the R. lateralis emerges from the Foramen suprapiriforme, runs downward and lateralward between the M. gluteus minimus and the M. gluteus medius and distributes to these two muscles. Its terminal branch emerges between the lateral margins of the M. gluteus medius and M. gluteus minimus, enters the M. tensor fasciae late from the medial surface at about the level of the middle of this muscle, and distributes to the M. tensor fasciae latae. At the same time it gives off small branches which reach the anterior marginal fasciculi of the M. gluteus maximus and is associated with the double innervation of the M. gluteus maximus. With reference to the distribution of the nerve to the M. tensor fasciae latae and M. gluteus maximus, the greatest number of cases (60%) were those in which division into the branch which distributes to the M. tensor fasciae latae and the branch which distributes to the M. gluteus maximus occurred after the branch to the lateral margin of the M. gluteus minimus was given off from the R. lateralis of the N. gluteus superior. Following this is the type (20%) in which the branch entering the M. gluteus maximus is divided from the branch entering the M. tensor fasciae latae. In only one case, the branch to the M. gluteus maximus could not be observed. Hepburn has from the findings obtained from anthropoid apes divided the M. gluteus maximus into three parts, that is, the M. gluteus maximus, M. tensor fasciae latae and what is called Agitator caudae or M. caudofemoralis which arises from the Tuber ischiadicum. The former two are connected with each other to some degree by fascia. Kleinschmidt combined the M. tensor fasciae latae and M. gluteus maximus to call them the M. gluteus superficialis and further divided the M. gluteus maximus into Pars superior anterior, Pars superior posterior and Pars inferior M. ischiofemoralis. Moreover, it is said that all of these parts are present in Chimpanzee

11 On the Muscles of the G1 uteal Region of the Macacus cyclopsis 11 and Gorilla, but Orang is said to be lacking the Pars superior anterior. According to this classification, in the Macacus cyclopsis the part distinguished as Pars inferior does not exist, Pars superior anterior and Pars superior posterior are completely adhered, and in all cases the lower part of the M. tensor fasciae latae and pars superior anterior are united with adhesion throughout the entire length. According to A p pel t o n, the condition in which a part of the fasciculi arising from the coccygeal vertebra is completely separated and independent to form the so-called M. caudofemoralis is considered the primitive form. This condition has been recognized in Tarsius, etc., but in the Macacus cyclopsis in this study this was not observed in any of the cases as in the case of the Macacus rhesus in 0 k u d a's study. Only two cases which showed a very slight indication of this were seen. In man the M. gluteus maximus is well developed, but in primates excluding Lemur and Hylobates (R a n k e) the M. gluteus medius is more strongly developed than the M. gluteus maximus. It is reported that the causes for the good development of the M. gluteus maximus are because it keeps the pelvis erect and because the caput femoris supports the entire body. In my findings the M. gluteus maximus is far weaker. There is a tendency in the primates for the origin from the coccygeal vertebra to be localized in comparison with that of man. It is reported that in Cebus apella the origin is from the first coccygeal vertebra, in Calithrix the 1st to 3rd coccygeal vertebra, in Cynocephalis the 1st coccygeal vertebra, in Cynopithecus the 1st and 2nd coccygeal vertebra, in Macacus rhesus the 1st and 2nd -coccygeal vertebra, in Hylobates the 1st coccygeal vertebra, and in Anthropoides from the entire coccygeal vertebrae (R a n k e, M i c h- a 1 i 5, Ha w e r & St r au s, 0 k u d a). The origin in the Japanese fetus is said to be not very different from that of the adult, arising from the posterior surface of all the coccygeal vertebrae. However in view of fact that the greater number of Macacus cyclopsis in this study have the origin localized to the first coccygeal vertebra, and that only one portion (24%) of the cases have the origin extending to the transverse process of the second coccygeal vertebra, it can be said that the origin of the Macacus cyclopsis is very much localized. With reference to the tendinous origin, the aponeurosis of the M. gluteus maximus is made up of fibers centering around the Spina iliaca anterior superior and Spina iliaca posterior superior

12 12 Masatada Sugiyama and radiate in a fan shape from the Crista iliaca and since its direction was sometimes found to be different from that of the muscle fibers, the finding coincided with that obtained by Blunt s c h l i that the aponeurosis of origin of the M. gluteus maximus is not a Regional fascia. With reference to insertion, it is reported that the insertion of the M. gluteus maximus is more distal in primitive animals (L o t h, Zielinsk a, H e p b u r n). In Lemur the insertion extends from the Condylus lateralis to the Trochanter major (R a n k e), in Cebus to the Condylus lateralis (R a n k e), in Cercopithecus down to the middle of the hemur (R a n k e), in Hylobates to the upper half of the femur (H e p b u r n, L o t h, Rank e), in Orang to below the Condylus lateralis (L o t h) or the middle of the femur (H e p- b u r Ti, Sonnta g, Rank e) and in Gorilla and Chimpanzee to the Condylus lateralis (H epbur n, Kohlbrugg e, Rank e), but in the Macacus cyclopsis in this study it extended to the lower lateral part of the Trochanter minor with no cases extending any further down. This resembles the findings obtained in Cynocephalis (M i c 1 i s). The insertion in human fetus is said to have no peculiar points in comparison with that of adult (M i u r a), but in Negroes (adult) it is that it extends to the middle of the femur (L o t h). In contrast with man, the Tuber ischiadicum of Primates is said to protuberate at the lower margin (medial margin) of the M. gluteus maximus and to adjoin with it (C hudzinsk i), but in my findings they are separated from each other and only in one case were they adjoined. With reference to its relationship to the M. tensor fasciae latae. the union between the two is said to be stronger in lower monkeys (Bluntschli, Riska, Michdlis, Hepburn), while Okuda has reported that in the Macacus rhesus they, viewed from the nature of the adhesion of the two, are not yet differentiated from the standpoint of phylogenesis and that the state of the M. gluteus superficialis could be observed. He also indicated that in many of them (67.5%) the anterior margin of the M. gluteus maximus is covered by the posterior margin of the M. tensor fasciae latae with adhesion or union with the M. tensor fasciae latae at the lower part of the iliac bone. In the Macacus cyclopsis of this study, union is similarly strong, but in all cases findings are different than that obtained by Okuda in that the anterior margin of the M. gluteus maximus covers the posterior margin of the M. tensor

13 On the Muscles of the Gluteal Region of the Macacus cyclopsis 13 fasciae latae. From the relationship between the M. gluteus maximus and surrounding muscles, Z i e 1 i n s k a has made a classification into four types, that is, (1) those in which there is a complete or partial adhesion with the M. tensor fasciae latae, (2) those in which there is an adhesion with the M. tensor fasciae latae with further adhesion at the lower part with the M. ischiofemoralis (Hapale), (3) those with adhesion with the M. ischiofemoralis (Chimpanzee) and (4) those in which it is completely separated (Orang and man). He further explained that Katarrhinen and Lemur belong with (1) and if this classification is followed, Macacus cyclopsis also belongs in (1). The existence of fasciculi at the separation region of both muscle mentioned by K o 1 e s n i k o w was also noted in rather high frequency (28%) in the Macacus cyclopsis. It is my finding on the nerve supply that in most of the cases there is double innervation by the N. gluteus inferior and the N. gluteus superior and that a separation of the N. gluteus inferior into two branches is noted. This double innervation is said to be a primitive form (B 1 u n t- schl i, G a d o w), while the separation of the N. gluteus inferior into two branches is not always evident in primates (K o 1 e s n i k o w). 2. M. tensor fasciae latae Origin : The M. tensor fasciae latae arises by a narrow muscular origin from the lateral margin of the iliac bone between the Spina iliaca anterior superior and Acetabulum border. The highest edge of the origin is higher than the origin of the M. gluteus minimus and M. Sartorius and its lower edge is lower than the lower edge of the origin of the M. sartorius. As for the accessory origins other than from the iliac bone, origin from the aponeurosis of the M. gluteus maximus (22%), origin from the M. gluteus medius (4%), and origin from the M. sartorius (2%) were noted. In addition division of the main fasciculi of origin was also noted (6%), but such division is a partial division limited to the area from the insertion to the upper one-third of the M. tensor fasciae latae. In one of these cases there was division at the posterior margin and the anterior margin of the M. gluteus maximus entered between this separated portion.

14 14 Masatada Sugiyama Insertion : At the upper one-third part of the lateral side of the femur, its posterior margin is covered by the M. gluteus maximus to which there is adhesion or union and after it becomes flat and it continues muscularly to the Tractus iliotibialis. The height of this continuation is lower than the insertion of the M. gluteus maximus into the Tractus iliotibialis. Relationship with the surrounding muscles : As its relationship with the M. gluteus maximus has already been discussed, this will only be briefly mentioned here. It was noted that lateral ventral surface of the M. gluteus medius and the posterior surface of the origin of the M. tensor fasciae latae were adhered, but in rare cases there was an accessory origin from the M. gluteus medius. The ventral surface of the M. gluteus minimus and the posterior surface of the origin of the M. tensor fasciae latae were found to be always strongly adhered. Adhered. to the ventral surface of the origin of this muscle is the M. sartorius and also with some frequency (26%) there was weak adhesion with the M. iliacus. Nerve supply : The R. lateralis of the N. gluteus superior, after sending off branches to the M. gluteus minimus and M. gluteus medius at between these two muscles, emerges immediately below the lateral margin of the adhesion between the lateral margins of both muscles, after which it divides into 2 or 3 branches to enter the medial surface at about the level of the central of the M. tensor fasciae latae. During this course send a small branch to the anterior margin of the M. gluteus maximus. In comparison with man, this muscle in primates is smaller. In Prosimians it is generally absent and in lower primates its development is said to be poor (H a w e r & S t r au s) ; in Gorilla and Chimpanzee weak fasciculus is reported to be present (H e p b u r n) ; and in Orang it is said to be absent (H e p b u r n, K l e i n s c h m i d t). The Macacus cyclopsis is no exception in the fact that its development is poorer in comparison with that in man. However, there was no case in the Macacus cyclopsis in whicb it was absent.

15 On the Muscles of the Gluteal Region of the Macacus cyclopsis 15 With reference to the origin of this muscle, in Chimpanzee, in contrast with the origin in man, the origin from the iliac bone is long and the undermost part is bordered by the M. sartorius (C h a m p n e y), but in the Macacus cyclopsis in this study it is still longer and its lower margin is lower than the lower margin of the origin of the M. sartorius. There are some cases (22%) in the Macacus cyclopsis in which there is accessory origin from the aponeurosis of the M. gluteus maximus and in a few cases there was accessory origin from the M. gluteus medius and the M. sartorius, but in O k u d a's report on the Macacus rhesus there is no mention of this point. The presence of such an accessory origin from the M. gluteus maximus in my cases, together with the strong union with the M. gluteus maximus which is always noted and the nerve supply to both muscles by the same nerve branch, is considered to sufficiently support the interpretation that this muscle separates from the M. gluteus maximus. The considerable number of cases with division of the origin in my cases was not reported in O k u d a's study of the Macacus rhesus. Concerning the insertion, in Tarsius it is said to be inserted with the Trachanter tertius (A ppelto n), but in my cases such an abnormality was not noted, for it continued muscularly with the Tractus iliotibialis at the upper third of the femur in all cases. Risk a has related that as this muscle is supplied by the N. gluteus superior its adhesion with the M. gluteus maximus is secondary. F u k u m o t o has concluded that since it is supplied by the N. gluteus superior in all cases in man this muscle should belong with the gluteal muscles. In view of my findings that it is supplied in all cases by the N. gluteus superior and that both muscles are strongly united, it is considered that his interpretation is proper. 3. M gluteus medius Origin : The M. gluteus medius which is the best developed muscle among the gluteal muscles, occupies the central part of the gluteal region, and arises muscularly from a large area over the upper half of the sacrum, while the medial part arises muscularly from the posterior surface of the sacrum and dorsal fascia. Insertion : In all cases it is inserted strongly muscularly into the upper

16 16 Masatada Sugiyama half of the Trochanter major and, at the insertion, adhesion with the joint capsule of this region is noted. In rare cases (10%) a portion of the medial fibers of insertion become a weak tendon and extended a little further downward. Relationship with the surrounding muscles Those with the closest relationship are the M. tensor fasciae latae, M. gluteus maximus, M. piriformis and M. gluteus minimus. The ventral surface of the M. gluteus medius is always strongly adhered to the origin of the M. tensor fasciae latae and the insertion of the M. piriformis ; the posterior surface of the M. gluteus medius is strongly adhered to the aponeurosis of origin of the M. gluteus maximus ; the outer margin of the ventral surface of the M. gluteus medius is adhered strongly by tendinous interdigitations to the posterior surface of the outer margin of the M. gluteus minimus. This adhesion with the M. gluteus minimus is more medial and stronger than the adhesion between this muscle and the M. tensor fasciae latae. Moreover, observed were cases (22%) in which the M. tensor fasciae latae arises from the aponeurosis of the M. gluteus maximus which is adhered to the M. gluteus medius ; cases (4%) in which the M. tensor fasciae latae arise from the posterior surface of the M. gluteus medius ; cases of mutual adhesion (4%) by the interlacing of muscle fibers of the surface of the origins from the iliac bone of the M. gluteus medius and M. gluteus minimus ; cases (2%) in which the fasciculi separated from the M. gluteus minimus is inserted into the ventral surface of this muscle ; and cases (20%) in which adhesion with the opposing surfaces of the M. piriformis and M. gluteus medius. The union with the M. piriformis at the insertion can always be noted, but in a few cases (14%) adhesion was noted throughout the length from the origin to the insertion. Nerve Supply : It is always supplied by the N. gluteus superior, but in some cases (46%) the N. piriformis is also distributed to this muscle. In case of this so-called double innervation, the N. piriformis generally penetrates the M. piriformis to enter the M. gluteus medius, but in very rare cases (2%) it is distributed to the M. gluteus medius without penetrating the M. piriformis. The N. gluteus superior distributes both the R. superior and

17 On the Muscles of the Gluteal Region of the Macacus cyclopsis 17 R. lateralis to the M. gluteus medius, but the R. superior divides into 2 or 3 branches above the R. lateralis to emerge at the Incisura ischiadica major. It further runs posteriorly or lateralward to distribute to the M. gluteus medius, while the R. lateralis runs lateralward between the M. gluteus minimus and M. gluteus medius to send of several branches to the M. gluteus medius. The N. piriformis enters the M. gluteus medius either after piercing the M. piriformis or without penetrating the M. piriformis but in all cases the area of distribution is the area of union between this muscle and the M. piriformis. The M. gluteus medius is stronger and larger than the M. gluteus maximus in almost all monkeys, but the origin and insertion are almost identical to that of man with few variation and, firm adhesion to the M. piriformis is noted in all cases. In Chimpanzee it is reported that the tendon of insertion is separated by the M. vastus lateralis which extends upward (H e p b u r n, S o n n- t a g), but in the Macacus cyclopsis of my study there was no case of such division of the tendon of insertion. With reference to its adhesion to the M. gluteus minimus, Hepburn has reported that in all anthropoid apes it is always completely separated from the M. gluteus minimus and R a n k e has said that both are united in Ilylobates which is a variation often seen in man, but in my findings firm adhesion with the M. gluteus minimus was noted in all cases similar to the findings of Okuda on the Macacus rhesus. In the Macacus rhesus it is said by some workers that the union with the M. piriformis is always present at the origin and the insertion (0 k U d a), while others (H o w e r & S t r au s) say that adhesion is noted only at the insertion. In my cases, union was noted in all cases at the insertion and a considerable number were adhered at the origin. Miyazaki has reported that in the Japanese the adhesion with the M. gluteus minimus is seen in 12.9% while union with M. piriformis is noted in 21.9%. 4. M. piriformis Origin : This muscle located on the ventral surface of the M. gluteus medius is a comparatively strong square-shaped muscle which always arises from the transverse process of the second and third sacral vertebra.

18 18 Masatada Sugiyama Insertion : The muscle fibers run downward and lateralward, unite with the ventral surface of the M. gluteus medius, and insert into the apex of the greater trochanter. Moreover, the lateral margin is generally longer than the medial margin. Relationship with the surrounding muscles : This muscle adjoins with the ventral surface of the M. gluteus medius and is adhered with it in various degrees. The portion below the center of the venter is always adhered to the M. gluteus medius, but a considerable number (20%) were found to have adhesion at the origin too and in the majority of these cases the adhesion or union extends over the entire length from the origin to the insertion. Moreover, in many of the cases (50%) this muscle is pierced by nerves, but none of the cases was pierced by the M. ischiadicus. However, in some cases (44%) this muscle was pierced by the N. piriformis which entered the M. gluteus medius, while in a small number (6%) it was pierced by the N. gluteus superior which entered the M. gluteus medius. Nerve supply : This muscle is generally supplied by only the N. piriformis (88%), but in a small number of cases (12%) there is double innervation by the N. piriformis and the N. gluteus superior and very rarely (2%) it is distributed by the small branches of the N. gluteus inferior. The N. piriformis emerges from the Foramen ischiadicum majus at the central part of the posterior side of N. ischiadicus, and enters the ventral surface of the M. piriformis near the origin of this muscle either as a short single branch (46%) or after separating into two branches (52%), but very rarely as three branches (2%). In cases where this nerve further distributes to the M. gluteus medius, it pierces the M. piriformis in many of the cases (44%) before supplying the muscle, but cases are very few (2%) where it distributes to the M. gluteus medius without piercing the M. piriformis. The area of the M. gluteus medius which is innervated in these cases is generally the area of union with the M. piriformis. With reference to the origin, it is reported that in the Macacus

19 On the Muscles of the Gluteal Region of the Macacus cyclopsis 19 rhesus it arises from the second sacral vertebra (0 k u d a) ; in the Hapale from the anterior margin of the sacrum (B eat t i e) ; and in the Chimpanzee, Orang, and Gorilla from the anterior surface of the sacram at the level of the second through fifth sacral bone (H e p b u r n) while some say that in Chimpanzee the origin is from the second to fifth. sacral vertebrae (C h a m p n e y). In comparison with these, in the Macacus cyclopsis it can be said that it is localized to the upper area as in the case of the Macacus rhesus. The nerve supply of the M. piriformis is said to be frequently related to the N. gluteus superior in man as in the case of the Macacus cyclopsis (R a n k e) and cases in which the N. ischiadicus pierces the M. piriformis have been relatively frequently noted (L o t h, Ad ac h i, Fukumot o, et al), but cases in which the muscle is pierced by the N. ischiadicus have not been noted in the Macacus cyclopsis. Cases in which the muscle is pierced by the N. cutaneus femoris posterior have been noted in man (K o n o), but such cases have not been discovered in my cases. 5. M. gluteus minimus The M. gluteus minimus is located beneath the M. gluteus medius. Origin: It always arises muscularly from a wide area over the lower half of the surface of the ilium, that is from the region below the origin of the M. gluteus medius. Of the fasciculi, that arising from the fossa iliaca descends almost perpendicularly, while that arising from the medial margin of the ilium descends lateralwardly so that it is fan-shaped converging toward the insertion. A relatively high frequency (20%) of incomplete division of the origin of this muscle was noted, the greater number of which being incomplete separation of the fasciculi arising from the medial margin of the ilium. There was only one case of separation of the origin from the fossa iliaca. Insertion : The fasciculi which converge in a fan-shape become a strong tendon which is inserted into the anterior lateral surface of the base of the greater trochanter, but a part of the lateral side is interposed between the origins of the M. vastus lateralis and M.

20 20 Masatada Sugiyama vastus medialis and descends along the lateral side of the greater trochanter to the insertion. Relationship with the surrounding muscles : This muscle is always adhered to the M. tensor fasciae latae and M. gluteus medius, but in addition there are cases (14%) in which it is weakly adhered to the posterior surface of the origin of the M. vastus medialis cases (6%) in which there is adhesion with the origin of the M. rectus femoris and cases (2%) in which there is adhesion with the M. vastus lateralis. Nerve supply This muscle is supplied by the N. gluteus superior. The R. lateralis of the N. gluteus superior, which emerges from the central part of the lateral margin of the Incisura ischiadica, descends lateralward between the M. gluteus minimus and M. gluteus medius and distributes to the M. gluteus medius and the M. gluteus minimus. The R. inferior, after leaving the lower margin of the Incisura ischiadica major, runs downward along the medial margin of the M. gluteus minimus to distribute to this muscle, but in a small number of cases (6%) it also distributes to the M. piriformis. According to literature, division of the M. gluteus minimus is often reported. Among them the most common is the division into two parts seen in Lemur, Gorilla, and Hylobates, while the division into three parts is said to be noted in Callithrix and Chimpanzee (H epbur n, Rank e, So n nt a g). The separation of the anterior fasciculi into an independent part which is the so-called M. gluteus quartus reported to be seen in Chimpanzee and Gorilla does not generally exist in lower monkeys (K ohlbrugg e), but is said to exist in very rare cases in the Macacus rhesus (0 k u d a). This was not seen in any of the Macacus cyclopsis in my study, but only some cases of incomplete separation of the origin were seen. 6. M. gemellus The M. gemellus is made up of a continuous muscular sheet and is not divided into the M. gemellus superior and M. gemellus inferior as in the case of man. Origin : At beneath the tendon of the M. obturatorius internus, the M.

21 On the Muscles of the Gluteal Region of the Macacus cyclopsis 21 gemellus arises from the Tuber ischiadicum and the posterior margin of Ramus superior ossis ischii. Its upper end is almost at the level of the Spina ischiadica. The fasciculi arising from the upper lateral margin of the Tuber ischiadicum is stronger and larger than the fasciculi arising from the Ramus superior ossis ischii below the Spina ischiadica, but in many of the cases these two form a continuous muscular sheet. That is, almost one-half (46%) were found to have no separation, but in the other cases (54%) only the muscle substance is divided into two but they all have connecting fascia on the ventral surface with no cases with complete separation into the upper part and the lower part. Insertion : The M. gemellus situate beneath the tendon of the M. obturatorius internus and encircles the upper and lower margins of the tendon to cover a part of its posterior surface to which there is always some degree of adhesion and is inserted into the Fossa trochanterica. Relationship with the surrounding muscles : The M. gemellus always encircles the edge of the tendon of the M. obturatorius internus to the posterior surface and in addition to its adhesion to some extent with this muscle in many cases it adheres with the joint capsule (28%), the insertion of the M. obturatorius externus (38%), and both the insertion of the M. obturatorius internus and the joint capsule (12%). Nerve supply : The M. gemellus is supplied by the R. lateralis of the N. puboischiofemoralis, but in rare cases (8%) it receives a branch from the R. medialis. The N. pubo-ischiofemoralis adjoined with the R. medialis and R. lateralis leves the Foramen ischiadicum majus and descends along the medial margin of the M. gluteus minimus, but as it approaches the lower margin of the M. gluteus minimus the R. medialis and R. lateralis become separated. Of these two branches, the R. lateralis at between the M. gluteus minimus and M. gemellus, near their margin of origin, enters from between these muscles into the ventral surface of the M. gemellus and in many cases after dividing into two branches it enters the upper surface of the M. quadratus femoris. The branches supplying the M. gemellus

22 22 Masatada Sugiyama appear to enter the pars superior and the P. inferior, respectively, but a sharp discrimination of the area of supply between the two could not be made. In primates, one or both parts of the M. gemellus may sometimes be absent or may form a continuous muscular sheet as in the case of monkeys (H a w e r & St r au s), but in all animals a muscle corresponding to the M. gemellus inferior is generally present and in accordance with orthograde and increase in muscle diameter at the pelvic outlet it is said that a muscle corresponding to the M. gemellus superior is formed (H e p b u r n). That is, in Chimpanzee and Gorilla it separates into two with the M. gemellus superior being larger than the M. gemellus inferior.(c ham pne y, Hepbur n, Sonnt a g) ; in Orang it separates into two with the M. gemellus inferior being larger (H e p b u r n, S o n n- t a g) and in the Macacus rhesus it generally forms a continuous muscular sheet, but in rare cases (5%) it is separated into the upper and lower parts and in some cases (7.5%) fassiculi separate from the deep side with the part corresponding to the M. gemellus inferior being larger (0 k u d a). In comparing these findings with those of the Macacus cyclopsis in my study, the findings are almost identical to that of the Macacus rhesus with the part corresponding to the M. gemellus inferior being large, but the incomplete type in which continuation is maintained on the ventral surface was seen at the same frequency as the continuous muscular sheet. Moreover, the upper end of the origin of this muscle is lower than that of the Macacus rhesus reported by 0 k u d a. In man this muscle is always separated into the M. gamellus superior and M. gemellus inferior, but in rare cases the M. gemellus superior is absent. There is a difference according to race regarding the absence. In occidentals its absence is comparatively high (Wood, 8%), but no case of absence has been noted in the Japanese (A d a c h i). The absence of the M. gemellus inferior is rarer than the absence of the M. gemellus superior (R aube r), but it is never absent in Macacus cyclopsis. In the Macacus cyclopsis this muscle is supplied by the R. lateralis of the N. pubo-ischiofemoralis and in some cases it has been noted that it is in addition supplied by a branch from the R. medialis. This finding together with the state of adhesion and separation of this muscle suggests as indicated by 0 k u d a that

23 On the Muscles of the Gluteal Region of the Macacus cyclopsis 23 the M. gemellus is separated from the same muscle mass as the M. obturatorius internus. 7. M. obturatorius internus Origin : The M. obturatorius internus is made up of the fasciculi arising from the inner surface of the pelvis and the fasciculi arising from the outer surface of the pelvis, that is, the Tuber ischiadicum, and they appear as if they were two independent muscles. That is, the fasciculi, which arise from the Membrana obturatoria, the ilium and pubis around the Foramen obturatum and as far anterior as the Symphysis pubica, pass over the posterior margin of the Ramus superior ossis ischii to emerge outside the pelvix and unite with the fasciculi which arise from the upper margin of the Tuber ischiadicum to appear at the posterior surface of the M. gemellus. Here it become tendinous and reaches the insertion as a flat thick tendon. Insertion : The tendon of insertion is always adhered to the M. gemellus at its ventral surface and both upper and lower margins and is strongly inserted into the Fossa trochanterica. Abnormalities such as division was not noted. Nerve supply : This muscle is supplied by the R. medialis of the N. puboischiofemoralis. That is, the R. medialis branching from the R. lateralis runs along the posterior side of the tendon of the M. obturatorius internus and here gives off branches to fasciculi of the M. obturatorius internus arising from the Tuber ischiadicum. The remaining part runs over the Ramus superior ossis ichii to enter into the pelvis and distributes to the fasciculi arising from within the pelvis. Rarely do the R. medialis distributes to the M. gemellus (8%). According to H e p bur n, in anthropoid apes in addition to the union with the M. gemellus, there is in all cases some adhesion between the tendon of the M. obturatorius internus and the insertion of the M. obturatorius externus. My findings also agree with his, but as in the case of Macacus rhesus (0 k u d a) there was no instance where the insertion is divided into two.

24 24 Masatada Sugiyama 8. M quadratus femoris The M. quadratus femoris is a thick square muscle which runs horizontally at the inferior anterior surface of the M. gemellus and can be divided into three surfaces. The superior surface faces the M. obturatorius externus ; the inferior surface is opposite the M. adductor magnus ; and the posterior surface has an incisure as the N. ischiadicus runs up and down at the central part. Origin : It arises muscularly from the lower lateral margin of the Tuber ischiadicum at the anterior side of where the M. biceps femoris arises and between the origin of the pars superior of the M. adductor magnus and the origin of the M. obturatorius externus. There is a rather marked tendency for this muscle to divide into two, but it is rare (4%) for it to separate completely, for in the most part (24%) there is separation only near the insertion with a rather good frequency (12%) showing merely a tendency of separation. Insertion : It runs horizontally and laterally to be inserted muscularly during its course to the Trochanter minor or Crista intertrochanterica. In the largest number of cases (68%) it is inserted only into the Trochanter minor, while in the other cases (32%) it inserted into the Trochanter minor and the Crista intertrochanterica, but among them there was one case where the muscle is divided to be inserted separately into the Trochanter minor and Crista intertrochanterica. Relationship with the surrounding muscles : There was no case in which it adheres with other muscles at the insertion, but it was noted that it was adhered with the M. biceps femoris (54%), M. semitendinosus (78%), M. semimembranosus proprius (64%), M. semimembranosus accessorius (6%), and M. adductor magnus (58%) respectively at the origin. Nerve supply : In all cases the R. lateralis of the N. pubo-ischiofeinoralis branches into two at about the central part of the superior surface of the M. quadratus femoris to enter and distribute to this muscle.

25 On the Muscles of the Gluteal Region of the Macacus cyclopsis 25 This muscle is sometimes absent in man (L o t h, A d a c h M i y a z a k i), but it is always present in the Macacus cyclopsis. With reference to its relationship with the surrounding muscles it is said that in the anthropoid apes this muscle generally has a close relationship with the M. gemellus inferior with complete union in some cases (H epbur n, S o n n t a g) ; in the Orang there is a considerable adhesion with the M. adductor magnus (S o n n t a g) ; and in Gorilla it is considerably united with the M. gemellus inferior and the M. obturatorius internus, and with its anterior part closely adhered to the M. obturatorius externus (R a v e n). In also the Macacus rhesus there is marked adhesion with the surrounding muscles and almost always it is adhered to the origin of the M. biceps femoris and the origin of the M. semimembranosus proprius (0 k u d a). In the Macacus cyclopsis of my study it is adhered with these surrounding muscles as in the case of the Macacus rhesus, but the adhesion in no case was of such a high degree which can be called union. In Chimpanzee, Orang, and Gibbon, the insertion is clearly divided into two ; one where the muscle is inserted perpendicularly into the posterior surface of the Trochanter minor and the other where it is inserted horizontally into the posterior surface of the femur (H epbur n), while in the Gorilla the insertion is limited to that in which the muscle is inserted vertically into the posterior surface of the Trochanter minor (H epbur n, Sonnta g), but in the Macacus rhesus the insertion is not divided into two (0 k u d a). In the Macacus cyclopsis of my study, in some of the cases the muscle is inserted into the Trochanter minor but in addition the superior fiber of this muscle is extended to be inserted into the Crista intertrochanterica in a considerable number of cases. Summary (1) M gluteus maximus The M. gluteus maximus arises by an aponeurosis from the entire length of the Crista iliaca and muscularly from the dorsal fascia of the posterior surface of the sacrum and coccygeal verte brae. In those cases in which the origin is the coccygeal vertebrae, it generally arises from the transverse process of the first coccygeal vertebra, but a considerable number was noted in which it arises from the transverse process of the first and second coccygeal ver-