ON ZOOLOGY. 



curious mechanism completely exposed to the 

 action of the air, through which it was rendered 

 fit to be returned to all the several parts of the 

 plant, for the purposes of support and nutrition. 



Animals require the aid of the same vivifying 

 principle, since they cannot live, if deprived of 

 atmospherical air. But as, from the peculiarity 

 of their structure, a much more complicated me- 

 chanism is requisite, and as the process is so 

 immediately connected with the first principles of 

 animal life, a brief account of it, I hope, will 

 not prove uninteresting. 



To illustrate the comparative importance of the 

 subject, I must again call your attention to the 

 nourishing principle of vegetables, in which the 

 food undergoes no preparatory process previously 

 to its being submitted to atmospheric agency, 

 but is absorbed from the earth in a fluid state, 

 and is at once conveyed to the leaves to undergo 

 the final preparation; while in animals, no less 

 than three very compound operations are requisite, 

 namely, mastication, digestion, and chylification, 

 before it be in a fit state to be submitted to that 

 atmospherical agency which is to impart the 

 nutritive property ; and this can only be effected 

 by the agency of two of the most important 

 organs in the animal body, namely, the heart 

 and lungs. 



Under this explanation, we are prepared to 



