SOS ANIMAL HEAT. 



not unreasonable to suppose, that by pursuing this line of in' 

 vestigation we may be enabled to arrive at some more precise 

 knowledge respecting the nature of respiration, and the pur- 

 poses which it answers in the animal economy. It would how- 

 ever be foreign to the plan of the present communication to 

 enter into any speculations on this subject, and I shall, there- 

 fore, only remark, that the influence of the nervous system 

 does not appear to be necessary to the production of the che- 

 mical changes, which the blood undergoes in consequence of 

 exposure to the air in the lungs*. 



The 



•The conclusion is directly contrary to that deduced by M. 

 Dupuytren, from a series of curious experiments, made with a view to 

 ascertain the effects which 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 what manner the apparently opposite 

 facts, observed by M. Dupuytren and myself, are to be reconciled 

 with each other. 



It was observed by this physiologist, that in an animal, in which both 

 the nerves of the par vagum are divided, the blood returned from the 

 lungs has a darker colour than natural, and that the animals, on whom 

 this operation is performed, die sooner or later with symptoms of 

 asphyxia, notwithstanding the air continues to enter the lungs ; and 

 hence he concludes, that the changes which are produced on the blood 

 in respiration are not the result of a mere chemical process, but are 

 dependent on the nervous influence, and cease to take place when the 

 communication between the lungs and the brain is destroyed. 



M. Provencal, in prosecuting this inquiry, ascertained that the 

 animals subjected to this experiment give out less carbonic acid than 

 before. 



M. Blainville observed, that the frequency of the inspirations is 

 much diminished ; and M . Dumas restored the scarlet colour of the 

 arterial blood by artificially inflating the lungs, and from these and 

 other circumstances, he has arrived at conclusions very different from 

 those of M. Dupuytren. 



My own observations exactly correspond with those of MM. Dumas 

 and Blainville. After the nerves of the par vagum arc divided, a less 

 quantity of carbonic acid is evolved, the inspirations are much 

 diminished in frequency, and the blood in the arteries of the general 

 system assumes a darker hue ; but its natural colour may be restored 

 by artificially inflating the lungs, so as to furnish a greater supply of air 

 to the blood circulating through them. 



We may suppose, that, on the division of these nerves, the sensibility 



of 



