SECTION I. 

 NUTRITION. 



CHAPTER I. 



PROXIMATE PRINCIPLES IN GENERAL. 



THE study of NUTRITION begins naturally with that of the proxi- 

 mate, principles, or the substances entering into the composition of 

 the different parts of the body, and the different kinds of food. In 

 examining the body, the anatomist finds that it is composed, first, 

 of various parts, which are easily recognized by the eye, and which 

 occupy distinct situations. In the case of the human body, for 

 example, a division is easily made of the entire frame into the 

 head, neck, trunk, and extremities. Each of these regions, again, 

 is found, on examination, to contain several distinct parts, or 

 " organs," which require to be separated from each other by dissec- 

 tion, and which are distinguished by their form, color, texture, and 

 consistency. In a single limb, for example, every bone and every 

 muscle constitutes a distinct organ. In the trunk, we have the 

 heart, the lungs, the liver, spleen, kidneys, spinal cord, &c., each of 

 which is also a distinct organ. When a number of organs, differing 

 in size and form, but similar in texture, are found scattered through- 

 out the entire frame, or a large portion of it, they form a connected 

 set or order of parts, which is called a " system." Thus, all the 

 muscles taken together constitute the muscular system ; all the 

 bones, the osseous system ; all the arteries, the arterial system. 

 Several entirely different organs may also be connected with each 

 other, so that their associated actions tend to accomplish a single 

 object, and they then form an "apparatus." Thus the heart, arte- 

 ries, capillaries, and veins, together, form the circulatory apparatus ; 

 the stomach, liver, pancreas, intestine, &c., the digestive apparatus. 

 Every organ, asrain, on microscopic examination, is seen to be made 



( 61 ) 



