55* GENERATION. S*CT. XXXIX. 



Secondly, there are new pans or new vefTels pro* 

 duced in many difeafes, as on the cornea of the 

 eye in ophthalmy, in wens and cancers, which can- 

 not be fuppofed to have had a prototype or original 

 miniature in the embryon. 



. Thirdly, how coutd mule-animals be produced', 

 which partake of the forms of both the parents, if" 

 the original embryon was a* miniature exifting in the 

 femen of the male parent ?' if an embryon of the- 

 male afs was only expanded, no- refsmblance to the 

 mare could exift hi the mule.* 



This miftaken idea of the extenfion of parts feems 

 to have had its rife from the mature man "refembling f 

 the general form of the fetus ; and from thence it- 

 Was believed, that the parts of the fetus were dif- 

 tended into the man ; whereas they have increafed 

 loo times in weight, as well as TOO times in fize ; 

 BOW no one will call the additional 99 parts a dif- 

 tendon of the original one part in refpecl: to weight. 

 Thus the uterus during pregnancy is greatly en- 

 larged in thicknefs and folidity as well as in capa- 

 city, and hence muft have acquired this x additional 

 fize by accretion of new parts, not by an extenfion 

 f the old ones ; the familiar a& of blowing up 

 the bladder of an animal recently flaughtered has 

 led our imaginations to apply this idea of diftention 

 to the increafe of fize from natural growth; whicb 

 however muft be owing to the apportion of new 

 parts ; as it is evinced from the increafe of weight 

 along with the increafe of dimenfion ; and is even 

 vifible to our eyes in the elongation of our hair 

 from the colour of its ends ; or when it has been 

 dyed on th head ; and in the growth of our nails 

 from the fpecks fometimes obfervable on them ; and 

 in the inereafe of the white crefcent at their roots, 

 and in the growth of new flefh in wounds, which 

 eonfifts of new nerves as well as of new blood-vef- 

 fels. 



