104 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



carbonic acid, and that the temperature of the lungs is not greater 

 than that of the rest of the body, this explanation had of necessity to 

 be dropped. 



Physiologists next transferred the seat of the combustion to the 

 blood ; but since then innumerable facts and experiments have shown 

 that it is in the tissues themselves, and not in the blood, that combustion 

 occurs. The methylene-blue experiments already described (p. 101) 

 show this ; and the following experiment is also quite conclusive. A 

 frog can be kept alive for some time after salt solution is substituted 

 for its blood. The metabolism goes on actively if the animal is kept 

 in pure oxygen. The taking up of oxygen and giving out of carbonic 

 acid must therefore occur in the tissues, as the animal has no blood. 



