OF THE 



[ UNIVERSITY j 



OF 



PHYSIOLOGY OF ALIMENTATION. 



CHAPTER I. 

 THE MECHANICAL PHENOMENA OF ALIMENTATION. 



i. The General Functions of the Alimentary Tract. 



Under the functions of the alimentary tract are included all the 

 functions of the hollow tube which begins with the mouth 

 ^and ends with the anus, together with certain of those of 

 the glands which pour their secretions into this tube. The 

 changes which the food undergoes in its passage through 

 this tube are in part purely mechanical such for example 

 as are the consequence of mastication or the movements 

 of the stomach in larger part, however, chemical. As an 

 example of the latter may be mentioned the conversion in 

 the stomach of albuminous bodies such as egg white into 

 the chemically less complex peptones*. Yet these chemical 

 changes are frequently associated with physical or physico- 

 chemical ones which from a physiological standpoint may 

 at times be quite as important as the chemical changes 

 themselves. 



We can classify the various substances which serve as 

 food under the general headings of proteins, carbohydrates, 

 fats, and inorganic substances. Under the first heading 

 fall, for example, the lean meats, the white of egg, etc., 

 while the chief representatives of the carbohydrates are 

 the starches and sugars which we consume. The fats are 



