APPENDIX. 169 



etables have formed part of the diet. In its progress 

 through the large intestine the food- mass loses still more 

 water, and the digestion of starcli and the absorption of 

 fats is continued. Finally the residue, with some excre- 

 tory matters added to it in the large intestine, is expelled 

 from the body. 



APPENDIX TO CHAPTER XII. 



The digestion and absorption of food are such fundamental facts 

 in physiology that a thoroughly intelligent comprehension of them is 

 of great importance; at the same time they are so largely merely 

 chemico-physical phenomena that they are readily illustrated by a 

 few simple experiments. These described below lake but little time 

 and cost but little money, while they cannot fail to be of value not 

 merely in interesting a class, but in giving its members a much better 

 idea of the way in which food is digested than they can get from 

 merely reading a book. 



1. Anatomy of the Alimentary Canal. Kill a rat by chloroform or 

 drowning. Dissect away the skin from the whole ventral aspect of 

 the body. 



Note in the neck region the large salivary glands which meet in the 

 middle line: the posterior gland, close to the middle line, rounded 

 and compact, is the submaxillary ; on raising it, its duct will be seen 

 passing forwards to the mouth, into which it may be followed by 

 separating the halves of the lower jaw. 



The large gland, composed of several loosely united lobes, and 

 reaching from the neighborhood of the ear to the submaxillary, is the 

 parotid. Its duct will be found passing forwards over the face to 

 the mouth, near the angle of which it passes in through the cheek 

 muscles. 



In front of the submaxillary will be found a small gland, the sub- 

 iinguaL 



Remove the muscles, etc., covering the larynx and trachea; cut 

 away the front and side walls of the chest and abdomen; remove 

 larynx, trachea, lungs, and heart. 



The gullet, a slender muscular tube, will now be exposed in the 

 neck; trace it through the chest; note the relative positions of the 

 abdominal viscera as now exposed, before displacing any of them; 

 then turning the liver up out of the way, follow the gullet in the 

 abdomen until it ends in the stomach. 



