^0 THE PHILOSOPHY 



itomach nor brain are eflential chara6lers which difcrimlnate 

 the animal from the vegetable. 



But all animals are endowed with fenfation, or at leaflt 

 with irritability, which laft has been confidered as a diftin£t- 

 ive character of animal life. Senfation implies a diftin^l per- 

 ception of pleafure and pain. We infer the exiftence of 

 fenfation in organized bodies, when we perceive that they 

 have organs iimilar to our own, or when they a(51:, in certain 

 circumftances, in the fame manner as v/e a6l. If an organ- 

 ized being has eyes, ears, and a nofe, we naturally conclude 

 that it enjoys the fame fenfations as thefe organs convey to us. 

 If we fee another being, whofe ftru^lure exhibits nothing 

 analogous to our organs of fenfation, contracting with rapid- 

 ity when touched, directing its body uniformly to the light, 

 feizing fmall infe£ts with teniacula, or a kind of arms, and 

 conveying them into an aperture placed at its anterior end, we 

 hefitate not to pronounce that it is animated. Cut off its 

 arms, deprive it of the faculty of contracting and extending 

 its body, the nature of this being will not be changed ; but 

 v/e will be unable to determine wdiether it poiTeiTes any 

 portion of Hfe. This is nearly the condition of the fmall 

 fe£lions of a polypus, before their heads begin to grow. The 

 wheel-animal, the eels in blighted wheat,and the fnails record- 

 ed in the philofophical tranfaCiions, afford inftancesof every 

 appearance of fenfation, or even of irritability,beingfufpended, 

 not for months, but for feveral years, and yet the life of 

 thefe animals is not extinguiflied ; for they uniformly revive 

 upon a proper application, of moifcure. 



Thefe and llmilar fa6ts fliow, that we are entirely ignorant 

 of the effence and properties of life. What life really is, 

 feems too fubtile for our underftanding to conceive, or our 

 fenfes to difcern. If we have no other criterions to diftinguifh 

 life, than motion, fenfation, and irritability, the animals juft 

 mentioned conti-nued for years in a ffate which every man 



