Medical Apparatuses 427 



ing appearance of the line of descent, according as it bends, becomes 

 straight, or oblique, or convex, or falls perpendicularly, shows us how 

 much more or less easily the blood passes through the capillaries. 

 The tracings of the pulse taken at normal atmospheric pressure, be- 

 fore entering the compressed air (tracings I - XVII of Vivenot) 

 show this more or less accentuated characteristic oscillation which the 

 finger detects only in the most pronounced cases, which is called 

 dicrotism, and which consists of two or, more often, three oscillations 

 of the wave. (P. 562) 



Whereas we have found polycrotism as a more or less marked 

 peculiarity of the normal pulse at ordinary pressure, it appears from 

 our curves that the compression of the air causes the polycrotism to 

 disappear and transforms the wavy line of descent into an almost 

 straight line or one which is more or less convex. 



So we find the proof of a congestion of blood in the vessels and 

 of a hindrance of the capillary circulation, in the descending line of 

 the curve as well as in its ascending part and its apex. 



Whereas, as Marey has shown and has proved by an example in 

 a tracing made in a case of heart disease (Fig. 86 of Marey), the 

 dicrotism is proportionately greater as the wave expelled by the 

 ventricle is smaller in proportion to the caliber of the artery, we con- 

 firm, for our part, this proposition in regard to the dicrotism, be- 

 cause, as it appears from the preceding discussion, the arteries, which 

 are compressed by the outer pressure and therefore convey very little 

 blood, are nevertheless very full of blood in proportion to their les- 

 sened caliber. 



Upon return to normal pressure, at once the original figure of the 

 line of descent reappears, and the simply convex line resumes its 

 previous polycrotism, or rather the form which has been produced per- 

 sists for a time, one or two hours, and then yields and gradually re- 

 gains its original appearance (See above, Fig. 9). 



In our analysis of the pulse tracings we have hitherto omitted 

 one circumstance, that is, the somewhat important change in the 

 amplitude of the curve under the influence of compressed air. 



For the sake of clarity, we have delayed analysis of it until we 

 reached the subject of the energy of the pulse, better named the size 

 of the pulse, which refers to the vertical height of the blood wave, 

 that is, the maximum height, and which, according to Marey, is pro- 

 portional to the energy of the pulsation. As we have concluded from 

 the agreement in the tracing of the curves which we have collected 

 for far, the amplitude of the pulse is lessened by the stay in com- 

 pressed air, and often loses from 4/5 to 5/6 of its original height, so 

 that the whole series of pulsations traced is often changed into a line 

 in which the separate waves are hardly perceptible. 



This decrease of amplitude is proportional to the compression of 

 the air and to the length of the stay in the compressed air, and so 

 the minimum amplitude is noted particularly at the end of the stay 

 in the compressed air; it happens by exception that after the return 

 to normal pressure the amplitude remains stationary, and returns 

 to the normal state after a long stay under ordinary pressure. It is 

 also exceptional to see the amplitude, after reaching its minimum, 



