SECT. XXXIX, 4- GENERATION. 567 



mals after their nativity, as in the preclusion of 

 the butterfly with painted wings from the crawling 

 caterpillar ; or of the refpiring frog from the fubna- 

 tant tadpole ; from the feminine body to the bearded 

 man, and from the infant girl to the la&efcent wo- 

 man ; both which changes may be prevented by 

 certain mutilations of the glands neceffary to repro- 

 duction. 



Secondly, when we think over the great changes 

 introduced into various animals by artificial or ac- 

 cidental cultivation, as in horfes, which we have 

 exercifed for the different purpofes of ftrength or 

 fwiftnefs, in carrying burthens or in running races ; 

 or in dogs, which have been cultivated for ftrength 

 and courage, as the bull-dog ; or for acutenefs of 

 his fenfe or fmell, as the hound and fpaniel ; or 

 for the fwiftnefs of his foot, as the grey-hound ; or 

 for his fwimming in the water, or for drawing fnow- 

 iledges, as the rough-haired dogs of the north ; 

 or laftly, as a play-dog for children, as the lap-dog ; 

 with the changes of the forms of the cattle, which 

 have been domefticated from the greateft antiquity, 

 as camels, and fheep ; which have undergone fo 

 total a transformation, that we are now ignorant from 

 what fpecies of \vild animals they had their ori- 

 gin. Add to thefe the great changes of lhape and 

 colour, which we daily fee produced in fmaller ani- 

 mals from our domeftication of them, as rabbits, 

 or pigeons ; or from the difference of climates and 

 even of feafons ; thus the fheep of warm climates 

 are covered with hair inftead of wool ; and the 

 hares and partridges of the latitudes, which are long 

 buried in fnow, become white during the winter 

 months ; add to thefe the various changes produced 

 in the forms of mankind, by their early modes of 

 exertion ; or by the difeafes occalioned by their 

 habits of life ; both of which became hereditary, 

 and that through many generations. Thofe who 



labour 



