3 8 8 GENER ATION. SECT. XXXIX. 4. 2. 



2. With this new organization, or accretion of parts, new 

 kinds of irritability may commence ; for fo long as there was 

 but one living organ, it could only be fuppofed to poflefs irrita- 

 bility ; fince fenfibility may be conceived to be an extenfion of 

 the effeft of irritability over the reft of the fyftem. Thefe new 

 kinds of irritability and of fenfibiiity in confequence of new or- 

 ganization, appear from variety of facts in the more mature ani- 

 mal ; thus the formation of the teftes, and confequent fecretion 

 of the femen, occafion the paflion of luft ; the lungs muft be 

 previoufly formed before their exertions to obtain frefli air can 

 exift , the throat or cefophagus muft be formed previous to the 

 fenfation or appetites of hunger and thirft ; one of which feems 

 to refide at the upper end, and the other at the lower end of 

 that canal. 



Thus alfo the glans penis, when it is diftended with blood, 

 acquires anew fenfibility, and a new appetency. The fame oc- 

 curs to the nipples of the breads of female animals ; when they 

 are diftended with blood, they acquire the new appetency of 

 giving milk. So inflamed tendons and membranes, and even 

 bones, acquire new fenfations ; and the parts of mutilated ani- 

 mals, as of wounded fnails, and polypi, and crabs, are reprodu- 

 ced ; and at the fame time acquire fenfations adapted to their 

 (ituations. Thus when the head of a fnail is reproduced after 

 decollation with a (harp razor, thofe curious telefcopic eyes are 

 alfo reproduced, and acquire their fenfibility to light, as well 

 as their adapted mufcles for retraction on the approach of 

 injury. 



With every new change, therefore, of organic form, or addi- 

 tion of organic parts, I fuppofe a new kind of irritability or of 

 fenfibility to be produced ; fuch varieties of irritability or of fen- 

 fibility exift in our adult ftate in the glands ; every one of which 

 is furnifhed with an irritability, or a tafte, or appetency, and a 

 confequent mode of aHon peculiar to itfelf. 



In this manner I conceive the veflels of the jaws to produce 

 the teeth, thofe of the fingers to produce the nails, thofe of the 

 fkin to produce the hair ; in the fame manner as afterwards 

 about the age of puberty the beard and other great changes in 

 the form of the body, and difpofition of the mind, are produced 

 in confequence of the new fecretion of femen ; for if the animal 

 is deprived of this fecretion thofe changes do not take place, 

 Thefe changes I conceive to be formed not by elongation or dif- 

 tention of primeval ftamina, but by appofition of parts ; as the 

 mature crab-fifth, when deprived of a limb, in a certain fpace of 

 time has power to regenerate it ; and the tadpole puts forth its 

 feet long after its exclufion from the fpawn j and the caterpil- 

 lar 



