700 Experiments 



disappeared and well-being was restored immediately. The pulse 

 rate— and this is a very exact indication— dropped immediately, to 

 return soon to its former figure. 



The graphs of Figure 57 show very clearly these curious 

 changes. The hours are marked on the horizontal axis. The upper 

 graph represents the downward course of the barometric pressure, 

 with the elevation corresponding to certain decompressions; the 

 lower graph indicates the variations in heart rate. At every breath 

 of oxygen, marked O, we see an instant fall of this latter line; 

 the demonstration is very clear. 



Such sudden modifications in the circulatory rhythm must 

 necessarily have ill consequences; it is to them that I attribute the 

 dizziness which accompanied each breath of oxygen. I add that on 

 the evening of this experiment for several hours I felt symptoms 

 of cerebral congestion which continued to annoy me somewhat. 



I wish the reader also to note the muscular trembling and the 

 strange state of mental weakness from which I suffered on reaching 

 the pressure of 420 mm., that is, about that of the elevation of 

 Mont Blanc; with a pencil in my hand, I was almost incapable of 

 multiplying 28 by 3. 



On the ninth of March, the next month, MM. Croce-Spinelli and 

 Sivel, who were planning ascents to a great height, came to my 

 laboratory with the purpose of studying upon themselves the dis- 

 agreeable effects of decompression and the favorable influence of 

 superoxygenated air. 



I can do no better than to reproduce the account which M. 

 Croce-Spinelli drew up for me immediately, from the notes which 

 he and M. Sivel took constantly in the apparatus, of phenomena 

 which they both experienced. 



Experiment CCLV. The diminution of pressure went on regu- 

 larly; in 35 minutes they were brought to 304 mm.; the return to 

 normal pressure was made in 22 minutes. They therefore re- 

 mained for 25 minutes below a pressure of 450 mm. 



Paris, March 10, 1874. 

 Sir: 



I am transmitting to you the data which M. Sivel and I collected 

 and the impressions we felt in your decompression bells, March 9, 

 1874. 



Emotion did not appreciably affect these observations, for I think 

 that none existed in M. Sivel, and it was extremely weak in me during 

 the whole experiment. The constant preoccupation of observing data 

 explains that well enough. 



The experiment began at 10:31. 



