Sudden Changes in Pressure 883 



when the animal was pregnant (Exp. DXXXVI) . The heart, which 

 continues to beat for a few minutes more, pumps into the arteries 

 the gases which its left cavities contained, although they are rarely 

 found there; the course of the venous blood, which continues a 

 little while, brings to the right cavities tiny bubbles of gas which 

 collect there in such quantity that a cat (Exp. DLXX) furnished 

 me with 33 cubic centimeters of it, and a little blood freed of 

 gaseous bubbles proceeds to the left heart by some of the pul- 

 monary arteries. The others are obstructed by the foam sent out 

 by the right heart. We find here the effects of this difficulty which 

 gases have in passing through the capillaries, difficulties which so 

 often cause the injections of anatomists to fail: we see bubbles of 

 gas refusing to pass through the lungs, and in certain experiments 

 we have seen the mesenteric arteries full of bubbles of gas without 

 the blood of the portal vein containing any. 



Let us suppose now the lightest case, either of an animal decom- 

 pressed from only 6 atmospheres (Exp. DXXX) , or, beginning with 

 10 atmospheres, of one decompressed very slowly (Exp. DLXXI, 

 DLXXVI, and DLXXVII) . In these cases, bubbles of gas will be 

 liberated, though smaller and much less numerous; those of the 

 venous system will stop in the lungs, and will cause some respira- 

 tory difficulties; then when they have been agitated and made ex- 

 tremely small (one sometimes needs the microscope to see them) , 

 they will reach the left heart and thence be pumped into the 

 arteries, where they will join those which spontaneously developed 

 there and which the circulation has not yet driven into the veins. 

 It may be that they will finally be redissolved without causing 

 any very definite symptoms; but if, unfortunately, some of them, 

 drawn by the circulation into the capillaries of the nervous sys- 

 tem, check locally the course of the blood there, immediately, in- 

 stantaneously, as in the experiment of Stenon, a paralysis or a 

 local excitation is the result; only in the case in point, the bubble 

 is so small that it soon disappears and everything returns to the 

 normal state. 



We understand that between these two extremes there must lie 

 many intermediary cases, and the experiments reported above pre- 

 sent plenty of examples. Nothing is more startling than to see 

 animals decompressed from 6 to 8 atmospheres leaping out of the 

 apparatus, as if delighted with their liberty, then seized after a few 

 minutes by a paralysis which always begins in the lower limbs, 

 but which often invades next all the rest of the body. 



Another surprising thing is this interval of 5 to 10 and even 15 



