EXPERIMENTATION AND PHYSIOLOGY 



air of animals. Lavoisier discovered nitrogen 

 (1775) and the composition of the air but he 

 believed that the carbon dioxid and the water 

 which were present in the expired air were due 

 to combustion of gases in the lungs. Vogel 

 and Hoffman found an excess of carbon dioxid 

 in the venous blood and an excess of oxygen 

 in the arterial blood, and physiology stood 

 upon the threshold of an understanding of the 

 principles of respiration. Later Magnus ex- 

 tracted and analyzed all of the gases of living 

 arterial and venous blood. Caisson disease is 

 now understood. To gain this knowledge ani- 

 mals had to be sacrificed. The mechanics and 

 chemistry of respiration being understood, 

 artificial respiration and the resuscitation of 

 the apparently drowned and asphyxiated be- 

 came an easy step. 



The struggle which man has had in order to Digestion, 

 acquire an understanding of the physiology of 

 digestion bears witness to the zeal for the truth 

 which is implanted in the human mind. To 

 begin with Spallanzani :- He caused hungry 

 animals to swallow small pieces of sponge 

 enclosed in perforated lead capsules, and after 

 a time, when the sponges had become saturated 

 with gastric juice, he removed them from the 



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