PREFACE. 5 



who was appointed during the late war by the medical 

 authorities at Richmond to report upon the condition of 

 the prisoners confined in the stockade. Such an opportunity 

 for observing the effects of improper and insufficient alimen- 

 tation upon large bodies of men has never been presented 

 before, and probably will never occur again. 



In studying the subject of digestion, many points pre- 

 sented themselves which were complicated by a mass of 

 conflicting observations and statements by the earlier 

 physiologists, and even by modern experimenters ; and there 

 are, even now, serious differences of opinion with regard to 

 some of the most important facts connected with this func- 

 tion. This is strikingly illustrated in the views of different 

 writers of high authority concerning the physiological prop- 

 erties of the saliva, the gastric juice, the bile, and the secre- 

 tion of the pancreas. Much of this confusion is to be 

 avoided, however, by treating of these questions upon the 

 basis of accumulated experimental facts, without regarding 

 mere opinions, even of the highest authority, when based 

 upon insufficient data. 



"With regard to absorption, very much has been devel- 

 oped within the last few years by accurate experimental 

 researches, in which some of the sources of error in the ear- 

 lier observations have been avoided, by remarkably success- 

 ful experiments upon living animals, and by the applica- 

 tion of improved methods for the analysis of the animal 

 fluids. Recognizing the importance of all these methods of 

 study, the author has endeavored to give the most extended 

 application of physical laws to the mechanism of absorption, 

 without losing sight of the fact that the physical phenomena, 

 presented in the living body are by no means fully understood. 



