292 CIECULATION. 



ever, lie takes no account of the results of this experiment, 

 which point conclusively to arrest of blood in the capillary 

 system, and the conclusions with regard to the effect of as- 

 phyxia upon the circulation are substantially those of Bichat. 



The immediate effects of asphyxia upon the circulation 

 are referable to the general capillary system. This fact was 

 demonstrated by experiments on the frog published in 1857. 1 

 In these experiments, the medulla oblongata was broken 

 up, and the web of the foot submitted to microscopic exam- 

 ination. This operation does not interfere with the circula- 

 tion, which may be observed for hours without difficulty. 

 The cutaneous surface was then coated with collodion, care 

 only being taken to avoid the web under observation. The 

 effect on the circulation was immediate. It instantly be- 

 came less rapid, until, at the expiration of twenty minutes, 

 it had entirely ceased. The entire coating of collodion was 

 then instantly peeled off. Quite a rapid circulation imme- 

 diately commenced, but it soon began to decline, and in 

 twenty minutes had almost ceased. In another observation, 

 the coating of collodion was applied without destroying the 

 medulla. The circulation was affected in the same manner 

 as before, and ceased in twenty-five minutes. 



These experiments, taken in connection with observations 

 on the influence of asphyxia upon the arterial pressure, con- 

 clusively show that non-aerated blood cannot circulate freely 

 in the systemic capillaries. 2 Yenous blood, however, can be 

 forced through them with a syringe, and even in asphyxia it 

 filters slowly through, and if air be admitted to the lungs 

 before the heart has lost its contractility, the circulation is 

 restored. 



No differences in the capillary circulation have been no- 



1 See article by the author, entitled "Phenomena of the Capillary Circula- 

 tion," American Journal of the Medical Sciences, July, 1857. 



2 In these experiments, ether had previously been freely applied to the surface 

 to render it certain that the effects on the circulation were not the result of this 

 ingredient of the collodion. 



