namely 7-9 %. later been confirmed by Tigerstedt(4). Knowing the amount of blood in the lungs and the time spent on

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1 ON THE AMOUNT OF BLOOD IN BY YAS KUNO. THE LUNGS. (From the Physiological Laboratory, Japanese Medical School, Mukden.) THE quantity of blood in the lungs has already been investigated by various authors. Spehl(1), for example, found in rabbits that the amount of blood in the lungs is on an average 7x1 % of the total quantity in the body. The results of Menicanti(2) who made his researches on a dog, rabbits, cats, and frogs agree on the whole with those of Spehl, namely 7-9 %. The time needed for the blood flow through the lungs has been measured by Stewart(3). His result was 3-4 sec. This figure has later been confirmed by Tigerstedt(4). Knowing the amount of blood in the lungs and the time spent on the flow through this organ we can easily calculate the time needed for one whole circulation through the body because the total amount of blood must pass once through the lungs. The result of such a calculation using the above figures does not agree with that recorded by other authors working with other methods of research. From the above figures, if we take 1/14 of the whole blood for the quantity in the lungs and 4 seconds for the time of the blood flow through the lungs, then the period of one whole circulation must be 56 sec. This figure is rather too high. Krogh(5) found that the blood flow through the lungs (the minute volume) in man varies between very wide limits (from 2' litres per minute) dependingon the conditions of the circulation. According to this result and assuming that the whole amount of blood in the body is 1/20 of the weight of the body, the time of one whole circulation must vary between about 8-6 and 60 sec. Thus the above figure (56 sec.) corresponds to that of the slowest circulation, but not to those of the faster ones which are often met with in normal life. In all the researches which were carried out by the above mentioned authors for determining the amount of blood in the lungs, animals with

2 BLOOD IN LUNGS. 155 open thorax were used. It is beyond question that the circulation is abnormally slow under such conditions. In order to accelerate the circulation either the amount of blood in the lungs or the quickness of the flow through the lungs or both must be increased. In -a paper lately published on the pulmonary circulation(6) I recorded that the fall of pressure in the pulmonary circulation varies with the volume of the venous inflow, i.e., it becomes smaller as the venous inflow increases. These results would seem to suggest that the pulmonary vessels were dilated when the circulation increased. I have therefore carried out some experiments to determine the amount of blood in the lungs under different conditions of the circulation. Method. All experiments were carried out on the heart-lung preparation (dogs). Changes in the circulation were brought about by increasing or diminishing the blood flow into the heart. In order to determine the condition of the circulation, the output of the left ventricle was measured, and also the pressures in the aorta and in the vena cava recorded. The rib-cartilages were cut away on both sides. Both lungs were simultaneously ligatured by means of a strong thread which was previously passed round the hilus. The artificial respiration was stopped just before tying off the lungs so that the lungs were always tied in a condition of expiration. I estimated the quantity of blood in the lungs, cut off in this way, by Welcker's method. I minced up the lungs in small pieces, washed with distilled water, then rubbed with glass powder in a mortar, and repeatedly extracted with water until the water was no longer coloured. This I carried out on both lungs separately. 1 c.c. blood was taken as a sample from the blood reservoir at the end of each experiment and diluted 200 times with distilled water. This solution served as the standard of comparison. The comparison of colour was made in two test tubes of exactly the same diameter (17 mm.). Previously I practised this method with defibrinated blood and found that the error in comparison of colour is certainly smaller than 6 %. 1. The amount of blood in the lungs. Table I gives the details of 5 of the 15 experiments which were made. In all cases the arterial pressure was kept at a height of mm. Hg and the pulse rate was from per minute. It is impossible to determine how much blood there is in the body of animals used for the heart-lung preparation. I therefore estimated it according

3 -156 YAS KUNO. to the weight of the animals. The amount of blood in dogs was determined by various authors by Welcker's method. Their results agree fairly well, namely 6*2-8-9 % of the body weight. According to the chemical method which is more indirect these figures may be somewhat too high. Since, however, the authors who recorded the amount of blood in the lungs used the results obtained by Welcker's method to express the percentage to the total amount of blood in the body, and since I also used Welcker's method in these experiments I will, for the present, assume the whole quantity of blood to be 7 % of the weight of the body and calculate the. percentage of the amount of blood in the lungs in relation to that in the body. TABLE I. Amount of blood in Weight Weight Height of Output Amount of lungs in of of Arterial venous Pressure per blood in percentage body heart B.P. reservoir v.c. minute lungs of that (kilos) (grins.) (mm. Hg) (ems.) (mm. H20) (C.C.) (C.C.) in body * *38 4* *44 According to these results the amount of blood in the lungs is, as I expected, much larger than the earlier authors recorded, i.e., it varies from % of the total amount of blood. The amount of blood in the lungs increases with the acceleration of the circulation, i.e., the amount of blood is about 2-2 times larger when the circulation is fast than when it is slow (calculated from the figures in Table I). If we divide the output of the left ventricle per minute by the amount of blood in the lungs, the quotient means the number of times the blood changes in the lungs per minute. In this way we can calculate the time of the blood flow in the lungs. This time is in Table I 3.8, 1*98, 1-82, 2'18, and 2-2 sec. In other experiments these figures varied between 1'9 and 4-1 sec. These figures are proportional neither to the output of the ventricle nor to the amount of blood in the lungs. Although I was very careful not to touch the lungs and kept them always moist with Ringer's solution during the operation, it was difficult to keep the lungs in the heart-lung preparation absolutely under normal conditions. Thus my results are in this respect not free from fallacy. But still I think I may justly maintain that the amount of blood in the lungs may be more than twice as great when the circulation is fast than when it is

4 BLOOD IN LUNGS. slow. And the time needed for the blood flow in the lungs is also more than twice as great when the circulation is slow than when it is fast. These results well agree with the necessities of life since the amount of blood which comes in contact with the alveolar air may be directly proportional to the rapidity of the blood flow, or even increase in a higher ratio. When the blood used for the heart-lung preparation is somewhat old, the lungs get into an cedematous condition. Although I am not sure whether this condition is really analogous to the cedema which occurs in pathological cases, I have investigated the amount of blood in the lungs of two dogs under such conditions. The circulation of patients with cedema of the lungs must be very slow. In order to imitate this condition I kept the venous supply to the heart very small in these experiments. The following protocol shows the results of one experiment: Dog. Weight 258 kilos, weight of heart 19 grms. Height of venous reservoir 6 cm. Arterial pressure 94 mm. Hg, venous pressure 20 mntn water, pulse rate 163 per minute, output of the left ventricle 124 c.c. per minute. The lungs swelled considerably. Weight of both lungs 130*5 grms. (the right lung 71, the left one 59B5 grms.). The amount of blood in both lungs 51*3 c.c. (right 29, left 22.3). The assumed amount of blood in the body 196 c.c. Therefore the amount of blood in the lungs is 26B2 % of the whole quantity of blood In the other experiment this percentage was 23-4 %. From these results it is evident that the lungs may contain about one-quarter of the whole blood under a pathological condition although the circulation is very slow. 2. The difference in the weight of both lungs. 157 The difference in size between the right and the left lung in dogs is very remarkable. The weight of the left lung varied in my experiments between 1: 1-2 and 1: 2-03 (average 1: 1.52) as compared with the right one. I measured the amount of blood separatelv in both lungs. Table II shows the weight and the amount of blood of the right lung and of the left one. As this table shows, the relationship between the weights of the lungs and. that between the quantity of blood contained in them is almost the same. This proves on the one hand that the blood is distributed uniformly in the lungs, and on the other hand that the method used for the determination of the amount of blood involves no considerable error.

5 158 Weight of riht lung left lung (grms.) (grm) YAS KUNO. Weight of right lung=weight of left lung multiplied by *42 1*47 1*48 1* Average 1652 TABLE II. right lung (ac.) * *05 Amount of blood in left lung (C.c.) * X * Amount of blood in right lung =Amount of blood in left lung multiplied by * * Average 1'55 SUMMARY. The amount of blood in the lungs was measured by Welcker's method on the heart-lung preparation (dogs) under different conditions of the blood circulation brought about by increasing or diminishing the venous supply. The amount of blood in the lungs increases when the blood circulation becomes more vigorous. Depending on these conditions, the amount of blood in the lungs varies from 8, % of the amount of blood in the body (assuming this to be 7 % of the weight of the body). If the lungs are cedematous they may contain about one-quarter of the amount of blood in the body. The ratio of the weight of the left lung to that of the right lung varies in dogs from 1: 1-2 to 1: 2-03 (average 1 :1.52). (1) (2) (3) (4) (5) (6) REFERENCES. Spehl. De la r6partition du sang circulant dans l'wconomie. Bruxelles, Menicanti. Ztschr. f. Biol. 30, S Stewart. This Journal, 15, p Tigerstedt. Skand. Arch. f. PhysioL 14, S Krogh. Skand. Arch. f. Physiol. 27, S Kuno. This Journal, 50, p