Medical Apparatuses 429 



according to certain changes in the attitude of the body, may display 

 a total or partial change in its form and in its direction. The first 

 case appears following a change of long duration in the blood pressure 

 and in the distention of the vessel, and is evidenced by a consider- 

 able modification of the whole line in reference to the original form 

 of the pulse, whereas a frequent change in blood pressure and vascu- 

 lar distension, such as takes place, for example, under the influence 

 of an irregular respiration, finds expression in the more or less 

 marked and more or less frequent incurvations in a series of rises 

 and drops of the pulse line. Now since this line, according to Marey, 

 indicates that an obstacle to the blood flow increases the distension in 

 the arterial system at some point, we had to investigate whether that 

 took place in compressed air because of the compression of the super- 

 ficial vessels, and whether the obstacle or the difficulty recognized 

 by us in the arterial circulation by the change in the line of ascent 

 also produced a change in our line of the whole, and found its ex- 

 pression in its rise (oblique ascent of the whole line) in compressed 

 air. 



After preparing the instrument for this purpose, according to the 

 rules established in our preceding experiments made with the use of 

 the sphygmograph, and arranging things in such a way that the reg- 

 istering stylus should be placed just in the middle of the band of 

 paper, at an equal distance from the upper and the lower edge, and 

 after releasing the clockwork, I thus made in the open air a tracing 

 of the pulse in the exact middle of the paper; but I did not have the 

 same success with operations in compressed air. Although the in- 

 strument had not been lifted, and no change had been made in the 

 attitude of the arm or the position of the instrument, the registering 

 stylus under the influence of the compressed air moved from its 

 original situation and rose; it even rose so high that it passed above 

 the upper edge of the paper band, and it had to be lowered, by a 

 slight movement of the hand, to the level of the paper so that a 

 tracing could be obtained. By this experiment we demonstrated: 

 for the radial artery a general rise of the blood tension and of the 

 vascular distention independent of that which can be observed in an 

 isolated pulsation. 



As far as concerns the influence of the respiratory movements 

 shown by the arched incurvations of the pulse line, it is slight and 

 imperceptible enough to go unnoticed by superficial observation. It 

 is very apparent only when one takes deep inspirations and when 

 there is a difficulty in respiration. 



In consequence of changes produced in the size of the thorax 

 by the inspirations and expirations on the one hand, and, on the 

 other, as a result of the rising and falling of the diaphragm, which 

 alternately contracts and enlarges the abdominal cavity and Ihe 

 thoracic cavity, and of the consequent change in distention of the 

 abdomen, a stronger pressure is produced alternately in the thoracic 

 aorta and the abdominal aorta; the result is a variable distention in 

 these vessels which is then communicated to the remote arteries. 



And so, as I have shown elsewhere, under the influence of com- 

 pressed air, we observe a slackening of the frequency of the respira- 



