174 THE POPULAR SCIENCE MONTHLY 



AN AMEEICAN CONTEIBUTION TO THE HISTORY OF 

 THE PHYSIOLOGY OF DIGESTION 



By Pbofessok LAFAYETTE B. MENDEL 



SHEFFIELD SCIENTIFIC SCHOOL OF TAIJi; DNIVEESITY 



MY interest has lately been aroused in reading a little American 

 monograph published over a hundred years ago as a disserta- 

 tion submitted for the degree of doctor of medicine to the faculty of 

 the University of Pennsylvania. It is entitled : " An Experimental 

 Inquiry into the Principles of Nutrition and the Digestive Processes," 

 by John P. Young, of Maryland (submitted June 8, 1803). ^ The 

 essay does not appear to have received notice from the writers of that 

 period; nor was there, probably, more occasion for calling attention to 

 this monograph than to the usual doctor's thesis of the present day. 

 Dr. Young's contribution, nevertheless, seems noteworthy because, in 

 examining the knowledge of digestion then current, he applies the test 

 of experimental evidence obtained at first hand — a sort of critique less 

 in vogue in his day than in ours. On the title page he quotes from 

 Lavoisier : " We ought in every instance to submit our reasoning to 

 the test of Experiment, and never to search for truth, but by the nat- 

 ural road of Experiment and Observation." The dissertation further 

 possesses a value, aside from its intrinsic merit as a scientific inquiry, 

 in giving some indication of the status of physiological studies in 

 America at the opening of the nineteenth century and in the first 

 medical college of this country. To appreciate Dr. Young's mono- 

 graph in the light of those times one must indulge in a moment's 

 retrospect. 



The history of the physiology of digestion may conveniently be 

 divided into three periods. The first of these embraces the earlier 

 days of science until the publication of Haller's " Elementa Physiolo- 

 gise " (1757), when theory and debate still maintained the triumph 

 of the " animal spirits " and the various conceptions of " vital prin- 

 ciples." In the succeeding epoch Reaumur (1752), Stevens (1777) 

 and Spallanzani (1783) put into practise the teaching of Bacon: 



Non fingendum aut excogitandum, sed 

 quid natura faciat observandum. 



^ I am indebted to Dr. C. F. Langwortliy, of Washington, for directing my 

 attention to this paper. It is reprinted in the Medical Theses, edited by Charles 

 Caldwell, M.D., Philadelphia, Thomas and William Bradford, 1805, which was 

 obtained for the Yale University Library through the courtesy of the Library 

 of the Surgeon General's Office in Washington. 



