CHAPTER IX. 



NUTRITION, DIETETICS AND ANIMAL HEAT. 

 NUTRITION. 



ALL the processes of the body as digestion, absorption, secre- 

 tion, circulation, respiration, etc. have a single object, viz., the 

 nutrition of the cells of the body. 



The ultimate source of all nutriment is, of course, food and 

 oxygen. The oxygen has been followed from the lungs to the 

 tissues as oxyhemoglobin of the blood. The various foods have 

 been seen to disappear from the digestive tract and to be con- 

 veyed to the tissues by the great nutritive fluid, some in recog- 

 nizable and some in unrecognizable form. If, now, we shall be 

 able to discover in what way these different materials thus fur- 

 nished the cells are utilized and appropriated by them, and in 

 what condition they subsequently escape from the system, the 

 study of nutrition will have been rendered much clearer. The 

 intake is through the lungs and alimentary canal; the output is 

 mainly by the lungs, skin, kidneys, and intestines. To show for 

 the changes which take place while the food is in the body there 

 is the growth of the body, the maintenance of tissue integrity, 

 secretion, heat, motion and nervous energy. 



It may be said at once, however, that the exact method of 

 appropriation of nutritive material by the tissues is a subject of 

 speculation, since it involves the question of life itself; and we 

 shall have to be content with recounting some of the condi- 

 tions influencing and some of the phenomena attendant upon 

 the process. 



171 



