CHAPTER II. 



PHYSIOLOGY OF DIGESTION IN THE SEVENTEENTH 

 AND EIGHTEENTH CENTURIES 



The circulation of the blood was worked out and proclaimed to 

 the world by one man, and his work was so complete that it has not 

 been rendered obsolete by subsequent knowledge. The history of the 

 physiology of digestion has been of gradual growth so that no one 

 man can claim credit for our present knowledge. Before the develop- 

 ment of chemistry, any marked progress in the physiology of alimen- 

 tation would not have been possible; the early workers in this par- 

 ticular field were chemists rather than physiologists. The history 

 of physiology during the seventeenth and eighteenth centuries in- 

 volves the lives and work of numerous investigators, each accomplish- 

 ing all that was possible considering the advancement of the general 

 scientific knowledge of the time. 



Two names of the latter part of the seventeenth and early part 

 of the eighteenth century are prominent as exerting important infl- 

 ence in the way of solution of the chemical problems of physiology. 

 These were George Ernest Stahl and Hermann Boerhsa-^T'^^hf was 

 born at Anspach in 1660 ; he studied at Jena, and after graduating be- 

 came court physician at Weimer, and in 1694 professor of medicine at 

 Halle. He died in 1734 in Berlin, where he moved in 1716 on his ap- 

 pointment as physician to the King of Prussia. Stahl was an ac- 

 complished chemist of his day. His views on gastric digestion may be 

 summed up in the following sentence from his work: "Some people 

 suppose that gastric digestion results from the action of particular 

 and specific ferments, and indeed go so far as to regard the stomach 

 as not only the seat but also the origin of a particular ferment, 

 whereas in the whole construction of the stomach nothing particular 

 is observed which would render the elaboration of such a special 

 agent likely." He was a firm believer in the psyche of Aristotle and 

 introduced a principle which he termed anima. He was wholly out of 

 sympathy with those who tried to explain the physical and 

 psychical phenomena of life and mind on chemical and mechanical 

 principles. He could not think of himself as a chemical retort subject 

 to ferments. The soul was to him the living force of the body; "It 

 was susceptible of being played upon by a thousand different influ- 

 ences, such as joy, sorrow and grief, love and friendship, the beauti- 

 ful, the true, the reverent, the sublime. * * * Can these things be the 

 product of chemical acids and alkalies and the mechanical devices of 

 the mason and builder ?" Sir Michael Foster sums up the teaching of 

 Stahl thus : "Learn as much as you can of chemical and physical pro- 

 cesses, and in so far as the phenomena of the living body exactly re- 

 semble chemical and physical events appearing in non-living bodies, 

 you may explain them by chemical and physical laws. But do not 

 conclude that that which you see taking place in a non-living bodj" 

 will take place in a living body, for the chemical and physical phe- 

 nomena of the latter are modified by the soul. The events of the bod^ 

 may be rough hewn by chemical and physical forces, but the soul will 



