O F A N I M A L S. 53 



this kind ? Is it an cftabliihed facl, that the male 

 fluid enters the uterus ? &c. 



To the lirft queftion 1 reply, that, if what I 

 had faid concerning the penetration of the in- 

 ternal mould by the organic particles, in growth 

 and nutrition, had been properly underRood, it 

 would be ealy to conceive, that, when thefe 

 particles are unable to penetrate the parts into 

 which they formerly entered, they, mull take 

 another route, and, of courfe, arrive at fom.e 

 other part, as the tefticlcs and feminal veilels. 

 Every attempt to explain the animal oecono- 

 my, and the various motions of the luiman 

 body, by mechanical principles alone, mud be 

 vain and inefleclual ; for it is evident, that the 

 circulation of the blood, mufcular motion, and 

 other fundlons of an animated body, cannot be 

 accounted for by impulfion, or by any of the 

 common laws of mechanifm. It is equally evi- 

 dent, that growth and reproduction are efFeds 

 of laws of a different nature. Why, then, do 

 we refufe the exiftence of penetrating forces 

 which ad upon the whole fubfiances of bodies 

 when we have examples of fuch powers in gra- 

 vity, in magnetic attradion, in chemical affini- 

 ties ? Since, therefore, we are affured by fads 

 and by a number of conflant and uniform ob- 

 fervations, that there are powers in nature wliich 

 ad not by impulfion, why are not thefe powers 

 ranked among mechanical principles ? Why do 

 Vfc rejed tliem in the explanation of eifcds 



^ 3 which 



