ANATOMY AND PHYSIOLOGY 



to do with the functions of living tissues; and it was 

 largely through their efforts and the labors of their fol- 

 lowers that the prevalent idea that vital processes are 

 dominated by unique laws was discarded and physiol- 

 ogy 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 

 possible the inroads into the unexplored fields of physi- 

 ology that were effected towards the middle of the 

 nineteenth century. 



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 



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