PROOF OF THE ACT OF NUTRITION. 



7. Brute bodies, as stones and minerals are not nourished. 

 The materials of which these are composed remain the same as 

 long as they exist, and if their volume increase it is simply by 



-the juxta-position of substances of the same nature as their own. 



8. But animals and plants on the contrary grow by intux'tus- 

 cfption, that is to say, by the deposite of new particles within 

 their very substance. 



9. The continual process of composition and decomposition 

 which constitutes the nutritive act, is not perceptible to our 

 senses ; but observations have been made which remove all doubt 

 of its existence, even in the bones, the hardest and deepest seated 

 parts of the body. An English surgeon, Belcher, eating of a pig 

 which had been fed by a dyer, remarked that the bones of the 

 animal were red, and attributing this peculiarity to the colored sub- 

 stances which it had eaten, conceived an idea that analogous 

 means might serve to render visible the effects of the nutritive 

 act ; he made experiments which, repeated by a number of 

 learned men, were crowned with entire success. 



10. After feeding animals on madder for a certain time, it is 

 always found that the bones are stained red by a deposite of this 

 coloring matter in their substance ; and after having thus fed an 

 animal, and then suspending the use of the madder, it is found, 

 after a certain period, that the red matter which must have been 

 deposited in the substance of these organs, is no longer there, but 

 has been, as we must conclude, ejected. Now, these facts may 

 be explained by the continuous process of composition and de- 

 composition, to which is given the name of nutrition. 



1 1. This renovation of the constitutent materials of the body 

 is indispensable to the continuance of life: when it stops in an 

 organ, that organ decays, and when it ceases throughout, death 

 soon follows. 



12. The nutrition of organised bodies is effected by the aid of 

 a liquid which conveys into all the organs, the necessary ma- 

 terials for their sustenance, and which serves at the same time, to 

 carry away from their substance those particles which are detached 

 hy the nutritive act, and destined to be expelled from the body 

 lii plants, this liquid is the sap, and in animals it is the blood. 



7. Are sto >i< s nourished ? How do they increase in size ? 



8. How do animals and plants grow in size? 



9. Is the nutritive act perceptible to ourselves? 

 JO. How was it proved? 



11. What is the consequence if nutrition ceases in an organ? If in aU 

 the organs? 



12. How is the nutrition of organized bodies effected? What are the 

 names 01 this liquic * 



