656 



PHYSIOLOGY. 



heart and lungs, but the capillaries of the head 

 as well. The mean of six experiments gives 

 the time of circulation in the dog as 17'5 sec- 

 onds, during which the heart made 51*5 pulsa- 

 tions. In the rabbit the time of circulation 

 was 11 seconds, during which there were 31 

 heart-beats. 



The velocity of the pulse-wave has been the 

 subject of special experiments by Dr. A. T. 

 Keyt, of Cincinnati. The general result of 

 previous experiments on this point by Conti- 

 nental physiologists has been to show that the 

 speed with which the pulse-wave travels is 

 about 20 feet per second ; and it has been fur- 

 ther known that the rapidity of the progress 

 of the wave is essentially dependent on the 

 rigidity of the tubes through which it travels. 

 But little had been done to determine the ef- 

 fect of other conditions modifying its speed. 

 Dr. Keyt, with improved apparatus, first set 

 himself to determine the precise influence of 

 tubes of different degrees of stiffness or elas- 

 ticity on the velocity of the liquid waves sent 

 along their interior. He selected for this pur- 

 pose, first a glass tube, then India-rubber tubes 

 of varying strength &nd firmness of wall, then 

 tubes made of chicken- gut, and finally the 

 aorta of a calf. These experiments demon- 

 strated that the velocity of liquid waves in 

 elastic tubes is proportional directly to the 

 stiffness and inversely to the elasticity of the 

 tube traversed ; and, as bearing on the rate of 

 pulse propagation in living arteries, they indi- 

 cate the important modifying influence which 

 the state of the arterial walls, as to stiffness or 

 elasticity, must exert upon the same ; for while 

 in a glass tube of T \ of an inch bore and 6 feet 

 in length, the wave- velocity was 216 feet per 

 second ; with firm India-rubber tube it was 

 165 feet ; with a softer and more yielding tube 

 of the same bore and length, it was 72 feet; 

 with a still thinner tube, 51 feet; with a simi- 

 lar soft tube, steeped in gasoline and thus ren- 

 dered more supple, 31 feet ; with a tube made 

 of India-rubber cloth, 28 feet ; with chicken- 

 gut, 16 feet ; and with a calf's aorta, 12-75 feet. 



Haemoglobin forms about 90 per cent, of 

 the dried red corpuscles, and is the substance 

 with which oxygen is associated in the blood, 

 and by means of which it is conveyed to the 

 tissues. It is characterized by the facility 

 with which it is decomposed into the proteid 

 globulin and the reddish-brown powder ha3ma- 

 tin, and by the readiness with which it takes 

 up oxygen to form a weak compound, without 

 undergoing any intrinsic change. The hgemo- 

 globin of human blood has been considered 

 very difficult to obtain in a crystalline form. 

 Dr. Robert Saunders Henry, of Charleston, W. 

 Va., has, however, in experimenting with hu- 

 man blood disgorged by leeches, after it had 

 remained in their stomachs for a time, found 

 haemoglobin already produced in crystals. 



The physical character of the proteids of 

 serum has been made the subject of investi- 

 gations by Mr. W. D. Halliburton, of Uni- 



versity College, London. Two of these pro- 

 teids have generally been recognized, which 

 the author designates as serum globulin and se- 

 rum albumen. The investigations were main- 

 ly directed to the latter body. In the first ex- 

 periments, which were made with the serum 

 of a dog, the serum albumen was found to be 

 divisible into three proteids. Subsequent ex- 

 periments showed that similar bodies were 

 found in the serum of other animals. Three 

 varieties of serum albumen were, therefore, 

 determined, which were called serum albumen 

 a (coagulating at 70-73 C.), serum albumen 

 (coagulating at 77-78), and serum albumen y 

 (coagulating at 80-82 C.). Nearly uniform 

 results were obtained with the serum of the 

 dog, man, monkey, rabbit, pig, and horse. The 

 serum globulin appeared to be in all the cases 

 a single proteid, while the serum albumen was 

 split up into three. But in the serum of the 

 ox, sheep, and horse, while the result was the 

 same in other respects, only two proteids were 

 obtained from the serum albumen, viz., those 

 coagulating at 77 C. and 84 C. It is inter- 

 esting to observe that these animals belong to 

 the ungulata. 



Special Senses. Experiments to determine 

 the law of the duration of color-impressions 

 upon the retina have recently been made by 

 Prof. Edward L. Nichols. Plateau made re- 

 searches upon the persistence of vision more 

 than fifty years ago, and found that the dura- 

 tion of the impression made upon the retina 

 by light depends upon the composition of the 

 ray ; upon which principle he built up his theo- 

 ry of after-images. His discovery was partially 

 confirmed in the course of Emdmann's experi- 

 ments, and has been very generally accepted 

 by the writers on physiological optics. Yet 

 our knowledge of the manner in which the 

 duration of the retinal image varies with the 

 wave-length of the impinging ray had not ad- 

 vanced. Prof. Nichols's experiments were 

 made in the usual manner, with rotating disks 

 of different colors. Their result was to con- 

 firm, in the main, the results reached by Pla- 

 teau, and to show that the persistence of the 

 retinal image is a function of the wave-length 

 producing it, being greatest at the ends of the 

 spectrum and least in the yellow ; that it de- 

 creases as the intensity of the ray producing 

 the image decreases ; that the relative duration 

 of the impressions produced by the different 

 spectral colors is not the same for all eyes ; that 

 each wave-length of the visible spectrum pro- 

 duces three primary impressions, red, green, 

 and violet, of which green disappears most 

 rapidly and violet is most persistent. Upon 

 the different rates at which these impressions 

 die away depend to a great extent the " sub- 

 jective" tints of moving objects ; and that the 

 duration of the retinal image depends upon 

 the length of time during which the eye has 

 been exposed, being very long after short 

 exposure, and approaching a definite mini- 

 mum value as the exposure increases. A minor 





