32 HUMAN PHYSIOLOGY 



for its ultimate destination, namely, the blood 

 current. In animals of simple organisation the 

 digestive system presents itself as a tube and 

 nothing more. In a worm, for example, it exhibits 

 pretty much the same calibre from one end to the 

 other, but in most animals the width of the tube is 

 found to vary in different sections of its length. 

 From the mouth we find the first part of the diges- 

 tive tube, called the cesophagus or gulltt (Fig. 6) lead- 

 ing as a tube directly to the stomach. The stomach 

 itself is often spoken of as a separate organ, and the 

 idea has thus arisen that the stomach resembles a 

 bag or sac depending in the interior of the body. 

 The true view of the stomach is that it is merely an 

 expanded part of the digestive tube; expanded, in 

 order that the food may remain in it for a time so 

 that certain important changes, to be hereafter 

 chronicled, may be effected upon it. Succeeding 

 the stomach we again come upon the tubular part of 

 the digestive system. This portion is termed the 

 intestine or bowel (Fig. 6). In man it is twenty-six 

 feet long, and is divided into two chief portions, 

 namely, the small bowel which immediately succeeds 

 the stomach, and which measures twenty feet in 

 length, and the large boivel forming the terminal 

 part of the digestive tube, extending in length to 

 about six feet. The digestive system, therefore, is 

 undoubtedly a tube, as has been described, with the 

 stomach as an expanded part thereof. 



DIGESTIVE GLANDS. The length and complexity 

 of the digestive system show a distinct relation to 

 the food upon which an animal subsists. The rule 

 may be remembered that vegetable-feeding animals 

 possess longer and more complex digestive systems 

 than do those which live on a carnivorous or flesh 



