XXX INTRODUGTOKY OBSERVATIONS. 



of its body. But the greatefl fingularity Is, th^t 

 certain parts Ihould be received, and others re- 

 jefted : that although the father is deprived of 

 thofe very parts which prove the offspring his, 

 it will have them all. Notwithftanding both pa- 

 rents fhould be maimed or mutilated, the germ is 

 perfeft, and the embryo will exhibit none of 

 thieir imperfedions. What an immenfe fund for 

 experiment and obfervation is here ! Sometimes 

 imperfeftions are . hereditary 5 but thefe are rare 

 and uncommon cafes : and it is much more re- 

 markable when an exifling imperfedion palfes 

 one generation and aflfeds the next. Deformity 

 of the perfon is often tranfmitted to a fucceeding 

 race : we have known a vice in the conformation of 

 the organs of hearing and fpeech in a whole fir- 

 mily, and fometimes feveral children born blind. 

 Thefe imperfedions, on inveftigation, are fre- 

 quently found in the relations of the parents. 



Confidering the little progrefs of knowledges 

 and the rude hypothefes of generation, it is not 

 at all furprifmg that the origin of animals was 

 afcribed to feminal vermiculi when they were 

 firft difcovered : and this would have acquired 

 additional credit had it been known there were 

 pores in the integuments of the germ or egg 

 which vermiculi might penetrate. — Let us con- 

 fider an impregnated egg. It confifts of a tran- 



fparent 



