Cotv-Pccl. 307 



vc'fTels nor valviilae in the interior of the chlorUlme mem- 

 brane j that is to fay, that which enclofes the yolk of the 

 esfo", 



10. That the chicken, confidered as foetus, is enveloped 

 in a peculiar membrane, that feparates it from the yolk, with 

 which it has a connection, and from the white, with which it 

 has none, and from which it is at a confiderablc diftance. 



11. That all fubilances deftined for the nourilhment of 

 this foetus are contained in diftinft capfuljE feparattd from it. 



12. That there exifts a perfeft analogy between the veflels 

 of the yolk and thofe of the placenta; and that the former 

 are to the yolk what the fecond are to the matrix, except the 

 difference in the circulation. 



13. That, contrary to the opinion of Haller, the albumen 

 docs not communicate with the aqueous bag ; and that the 

 chicken makes no ufe of this fluid for its nourifhment. 



14. During the latter period of incubation, everj' thing 

 left enters into the abdomen of the chicken in fuch a manner 

 that no umbilical cord remains without. 



15. That the red-blooded animals, which live in air, may 

 be divided into two grand clalTes, the umbilical and non- 

 umbilical. 



Dr. .Tenner has made an interefting difcovery in regard to 

 the cow-pock. He obferved that cows were fubjcch to puf- 

 tules on their teats. Thofe who milk them acquire puftules 

 alfo; and it is very extraordinary that by thefe means they 

 are preferved from the fmall-pox. He inoculated with the 

 cow-pock in the fame manner as with the common fmall- 

 pox, and by thefe means produced the fame efi'crts as when 

 people acquire the difeafe by touching the puftules of cows ; 

 that is to fav, thefe people are not liable to the common 

 fmall-pox, either by communication or inoculation. Thefe 

 facts have been confirmed by leveral other phyficians, fuch 

 as Drs. Pcarfon, Pulteney, &c. Dr. Wof)dvillc, phyfician 

 to the Small- Pox Hofpital, has inoculated in this manner 

 fevcral hundred perfons. This difcovery is of the utmoft im- 

 portance to himianitv ; for it is well known that the natural 

 fmall-pox is one of the moft deftrudivc of all thofe difeafes 

 R r a which 



