304 OF THE GROWTH, &c. 



latter feem to derive their origin from the for- 

 mer, and to be intended more for conferring 

 fymmetry and external ornament on the animal, 

 than for enabling it to exifl:, or to perform the 

 funt^cions efTential to life. Tbcfe two different 

 fpecies of parts are fuccefTively e^xpanded, and 

 are almoft equally apparent at the time of birth. 

 But there are other parts, as the teeth, vv-lfich 

 arrive not at full maturity till feveral years af- 

 ter; and otheis, as tlie glandulous bodies in the 

 female tefticles, the beard of malesy^c. which 

 appear not till the age of puberty. , 



To difcover the fundamental and elTential 

 pans of an animal body, attention muil: be had 

 to-the mimber,-fituation,. and nature cf the 

 v/hole. Thofe which are fimple, thofe whofe 

 pofition is invariable, and thofe without which 

 the animal cannot exift, muft neceflarily be the 

 moft efTential. Thofe, on the contrary, which 

 A4:e' dfeuble, or more numerous, thofe which 

 vary ifi fize and' pofition, and thofe which may 

 be taken away without injuring or killing the 

 creature, may be regarded as Icfs effential, or 

 more acceflbry to the animal machine. Ariflotle 

 mentions, that the only parts efTential to all ani- 

 mals are thofe with which they take and digeft 

 their nouriflimenr, and throw out the fuperfiu- 

 ous part of it from, the body. The whole in- 

 teftinal canal is indeed extrem.ely funple, and 

 no other part can (iipply its place. The head 

 and back-bone are likewife fimple parts, the po- 

 fition 



