212 



Analyses of Books. 



[Marches 



was necessary to ascertain in a more satisfactory manner than he 

 had done, how far the chemical changes which take place upon 

 the air in artificial and in natural respiration were of the same 

 extent. This is the object of the present paper. Seven expe- 

 riments are related, three upon rabbits in their natural state, and 

 four upon rabbits in which the fimctions-of the brain were de-- 

 stroyed or suspended. 



Most of our readers we presume know that the only sensible 

 change produced upon air by respiration is the conversion of a 

 portion of its oxygen into carbonic acid gas, without any change 

 in its bulk. If, therefore, the same proportion of oxygen be 

 changed into carbonic acid gas in both cases, then it follows that 

 the air has «jndt rgone the same chemical changes. The following 

 are the results of Mr. Brodie's experiments. 



Natural Respiration, 



1. A rabbit 50 cubic inches in bulk, converted in an hour 

 50 6 cubic inches of oxygen into carbonic acid gas. 



2. A rabbit of 48 cubic inches, in the same space of time con- 

 verted 5() 44 cubic inches of oxygen into^carbonic acid gas. 



3. A rabbit of 48 inches, produced in the same space of time 

 56*44 cubic inches ; or the same as the last. 



Artificial Respiration. , 



1. A rabbit of 50 cubic inches converted in an hour 40*48 

 cubic inches into carbonic acid. But in this case some blood 

 v/as lost, and the extent of the circulation was somewhat di- 

 minished. 



2. A rabbit of 45 cubic iijcbes produced in an hour 51'1 

 cubic inches of carbonic acid gas. 



3. A rabbit of 48 cubic inches produced in an hour 54*43 

 cubic inches of carbonic acid gas. 



4. A rabbit of 47 cubic inchrs produced in an hour 56*55 

 cubic inches of carbonic acid gas. 



Such are the results of Mr. Brodie's experiments. They seem 

 to make out his conclusion in a very satisfactory manner, that 

 the same chemical changes were produced upon the blood by 

 artificial respiration that take place during natural respiration. 

 Now, in all these cases, the thermometer sunk more rapidly nn 

 the animal subjected to arti^ciai respiration than in an animal 

 killed at the commencement of the experiment and placed in 

 the same circumstances. 



Are we then to give up the opinion that respiration produces 

 animal heat, and to conclude tliat the chemical theories of ani- 

 mal heat at present received are all erroneous ? The question is 

 of very difficult answer. Th.ere need be no very great hesitation 

 in admitting that Dr. Crawfordls experiments, which constitute 

 the foundation of his theory, are of too delicate a nature to ad- 



