38 A COURSE ON ZOOLOGY. 



cause the bile-duct becomes obstructed or the secretion 

 of bile is suspended, the elements of the bile are no 

 longer removed from the blood, and that liquid acquires 

 a characteristic yellow color, which is communicated to 

 the skin. 



The pancreas, which is analogous to the salivary glands 

 in structure, forms a sort of tongue lying against the 

 vertebral column, and behind and below the stomach. 

 Two ducts carry into the duodenum the pancreatic juice, 

 these openings being close by that of the gall-duct. 



It will be well to review the reciprocal relations of the 

 various organs contained in the abdominal cavity. (Fig. 

 20.) The stomach occupies the upper part to the left ; 

 the liver is to the right of the stomach, and somewhat in 

 front ; the spleen is left of the stomach and slightly be- 

 hind it; the transverse colon in front of it; the pancreas 

 below it ; the small intestine directly under it. The kid- 

 neys organs that excrete the urine are placed, one on 

 each side, in the lumbar region, and the bladder, the 

 common reservoir into which they discharge, fills the 

 front of the abdomen at the point corresponding to the 

 anterior junction of the bones of the pelvis. All these 

 organs are closely pressed together, and yet, by means 

 of the separating prolongations of the peritoneum, they 

 are perfectly isolated one from the other. 



Phenomena of Digestion. Some of the phenomena of 

 digestion are purely mechanical, relating to the division, 

 trituration, and forcing forward of the food ; others are 

 chemical, and these include all the transformations which 

 the food undergoes in its onward passage in order to 

 become fitted for absorption. 



These transformations must end in the rendering of 

 the food soluble, or, as in the case of fats, its division into 



