fS6 Medicine. 



body is owing to the gradual and successive changes 

 of arterial blood to venous throughout the body, 

 and of venous to arterial in the lungs. It is also 

 agreeable to this doctrine to suppose that the 

 higher temperature of some parts of the body may 

 be caused by arterial blood absorbing more carbon 

 and hydrogen, or, in other words, becoming more 

 rapidly venous. 



However ingenious this explanation deserves to 

 be regarded, it has not been deemed satisfactory. 

 The difference in specific caloric, admitting the 

 calculation to be accurate, is justly thought too 

 small to account for the great quantity of heat 

 which must be evolved. And if the opinion of 

 some be true, that the carbonic acid gas and water 

 emitted in expiration are not formed in the lungs, 

 but during the circulation, this doctrine must be 

 altogether untenable. 



This defect in Dr. Crawford's hypothesis might 

 perhaps be remedied, if Mr. Davy's supposition 

 of air entering the blood and combining with it in 

 the state of gas, should be admitted. In that case 

 it is evident that the air at first would only set free 

 part of its caloric, and that the remainder must 

 gradually escape in the successive stages of the cir- 

 culation. In another mode, likewise, that defect 

 has been attempted to be remedied. It has been 

 alleged, that the evolution of caloric attends almost 

 all chemical combinations; that all animal fluids 

 which pass through capillary vessels and glands, foi: 

 the purposes of secretion, are subjected to such new 

 chemical combinations, as must incessantly give 

 out heat; and that this glandular action thus ac- 

 -counts for the more general and copious source of 

 animal temperature. 



From the view of respiration now given, it re- 

 sults that the final causes of that function are these: 

 }, To complete the assimilation of the blood; 



