FUNCTIONS OF NUTRITION. 27 



LESSON II. 



Functions of Nutrition Nutrition of Organs Proof of the 

 *>ristence of the nutritive movement Coloring of bones The 

 blood is the principal agent of nutrition use <>f the blood study 

 of this liquid physical properties of the blood red and while 

 blood Globules Serum coagulation venous and arterial blood 

 'Iransformation of venous into arterial blood by the action oj 

 the air. 



OF THE FUNCTIONS OF NUTRITION. 



OP THE NUTRITIVE ACT. 



1. NUTRITION is the vital act by which the different parts o, 

 the bodies of organized beings renew the materials of which they 

 aj-e composed. 



2. To effect this renovation, the animal appropriates certain 

 substances within his reach, which are adapted to this purpose, 

 and these substances being introduced into the body and distri- 

 buted to the different organs, are there retained and become con- 

 stituent parts of them. 



3. At the same time that the organs thus acquire new mate- 

 rials, they lose others, which, having become old and useless, are 

 in some way detached and expelled. 



4. Thus, then, the new materials take the place of those which 

 have been detached from the organ, so that its substance is, little 

 by little, renewed. 



5. When a living being thus incorporates with its organs more 

 material than it loses, its volume augments, and of course its 

 weight increases: Thus, by the act of nutrition, the infant, 

 which at birth weighed only five or six pounds, is found to have 

 acquired, when it has reached the age of twenty-tive years, more 

 than a hundred weight, and a proportionate increase in size; but 

 if the contrary be true, and the living being loses more material 

 than it incorporates with its organs, it grows thin, as is often ob- 

 served when the adult approaches extreme age ; and when these 

 two phenomena are in just equilibrium, its weight remains the same 



6. This nutritive act takes place in all living beings. 



1. What is nutrition ? 



2. How do animals renew the materials of which their bodies are com- 

 posed ? 



3. Do the organs always retain the materials acquired ? 



4. Why is the size of the organs not increased by the constant accession 

 of new materials ? 



5 When an organ receives more material than it loses, what is the con 

 sequence ? When an organ loses more than it receives what happens ? 

 6. Does the act of nutrition take olace in all things 1 

 D2 



