412 



On the. Influence of the Brain 



The rabbil oociipicd the space of 47 cubic inches. 



502 + Hi 4- 2 i? JC9 



~Tr~~ ~ TiT" ^^'^'^ cubic inches of carbonic 



acid evolved in 30 minutes, which is at the rate of 56"55 

 cubic inches in an hour. 



The animal lay as if in a stale of profound sleep. At 

 the end of two hours and twentv minutes, from the time of 

 the poison being apj)lied, the therniometer in the rectum 

 had falltn to 79^ and he was again apparently dead; but 

 the heart still continued acting, though feebly, and its 

 action was kept up for 30 niinuten longxr by means of arti- 

 ficial breathing, when the iliermometer had fallen to 76°. 

 The carbonic acid evolved during these last 30 minul(!S 

 amounted to nearly 13 cubic inches. 



From the precauti'^ns with which these experiments were 

 made, I am induced to hope that there can be no material 

 error in their results. Thev appear to warrant the con- 

 clusion, that in an animal in which the brain has ceased to 

 exercise iis functions, although respiration continues to be 

 perlbrmed, and ihe cireula'ion of the blood is kept up to 

 the natural standard, although the usual changes in the 

 sensible qualities of the blood take place in the two capil- 

 lary systems, and the same quantity of carbonic acid is 

 formed as under ordinary circumstances ; no heat is gene- 

 rated, and (in consequence of the cold air thrown into the 

 lung>) the animal coals mure rapidly than one which is 

 acfuadv di ad. 



It is a circumstance deserving of notice, that so large a 

 quan.ilv of air should be consumed by the blood passing 

 through the hnigs, wlicn the functions of the brain, and 

 those of the organs dependent on it, are suspended. Per- 

 bap'' It is not unreasonable to su]ipose, that by pursuing 

 this line of investiiiatioii we mav be enabled to arrive at 

 .some more precise knowledge respecting the nature of re- 

 spiration, and the purposes which it answers in the afiimal 

 ceconomv. It WDuld however l)e foreiirn to the plan of the 

 present commiMiication to enter into any speculations on 

 this subject, and I shall thereh)re only remark, that the in- 

 fluence of the nervous system does not appear to be neces- 

 sary to the produition of the chemical changes which the 

 bio d uuiiergocs in consequence of exposure to the air in 

 the lungs*. 



The 



* This conclusion is directly coiUrarj' to that deduced by M Diipu/iren, 

 from a series of curious experiments, made witli n view to ascertain the 

 effects whieh follow the division of the nerves of the par vagum. and it is 

 an object of some importance in the present investigation, to ascertain in 



whiit 



