PROGRESS IN ANATOMY AND PHYSIOLOGY 



was brought within the recognized province of the 

 chemist. So at about the time when the microscope 

 had taught that the cell is the really essential structure 

 of the living organism, the chemists had come to under- 

 stand that every function of the organism is really the 

 expression of a chemical change that each cell is, in 

 short, a miniature chemical laboratory. And it was 

 this combined point of view of anatomist and chemist, 

 this union of hitherto dissociated forces, that made pos- 

 sible the inroads into the unexplored fields of physi- 

 ology that were effected towards the middle of our cen- 

 tury. 



One of the first subjects reinvestigated and brought 

 to proximal solution was the long-mooted question of 

 the digestion of foods. Spallanzani and Hunter had 

 shown in the previous century that digestion is in some 

 sort a solution of foods ; but little advance was made 

 upon their work until 1824, when Prout detected the 

 presence of hydrochloric acid in the gastric juice. A 

 decade later Sprott and Boyd detected the existence of 

 peculiar glands in the gastric mucous membrane; and 

 Cagniard la Tour and Schwann independently discov- 

 ered that the really active principle of the gastric juice 

 is a substance which was named pepsin, and which was 

 shown by Schwann to be active in the presence of hy- 

 drochloric acid. 



Almost coincidently, in 1836, it was discovered by 

 Purkinje and Pappenheim that another organ than the 

 stomach the pancreas, namely has a share in diges- 

 tion, and in the course of the ensuing decade it came to 

 be known, through the efforts of Eberle, Valentin, and 

 Claude Bernard, that this organ is all-important in the 

 digestion of starchy and fatty foods. It was found, too, 



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