424 



Historical 



curve is further prolonged backward ... so that the curve as a whole 

 assumes the form of the segment of a sphere. 



The changes which we have just described are proportional to 

 the strength of the air pressure and to the duration of the stay in 

 compressed air and consequently are more marked and more pro- 

 nounced as the air pressure is carried higher and the stay in the ap- 



Fig. 10 



paratus is lengthened. We find then that the indications produced 

 after twenty minutes of maximum pressure, that is, the visible ob- 

 liquity of the line of ascent, the shortening of the wave, the rounded 

 flattening of the top, and the transformation of the wavy line of 

 descent into a straight line or a simple convex line, after an hour 

 and a half, that is, after an hour of exposure to the constant maxi- 

 mum pressure, take on a still more evident character, so that the 

 tracing of the pulse finally presents, so to speak, only a straight line. 



Fig. 11 



In these four figures letter a indicates the sphygmographic 

 tracing obtained under normal pressure; b is the tracing while the 

 pressure is rising in the apparatus; c, during the period of constant 

 compression; d, after return to normal pressure. Fig. 11, ai was taken 

 while the pressure was increasing; Ci while it was decreasing. 



Upon return to normal atmospheric pressure, immediately after 

 the treatment, the curve resumes its original form, or only partially 

 returns to it, or, somewhat frequently, the change when it has once 

 begun in the blood curve undergoes a downward movement. Figure 

 9 expresses all these different phases. 



