t 



24 



UMBILICAL VESSELS. Sect.III. L4. 



of them an abforbent fyftem of vefTels, which imbibe the nutritious 

 matters laid up for them in the albumen or white of the egg, and in 

 the cotyledons or lobes of the feed ; and alfo of a placental fyftem of 

 arteries for the purpofe of oxygenating their fluids, as defcribed above 

 in the feed, and which appears in the egg to be fpread on a mem- 

 brane, which covers the white, as is (licvvn in the plates of Mai- 



pighi, and called by him the chorion, and expofes the blood of the 

 chick to the oxygen of the air contained at the broad end of the egg 

 through a moift membrane. 



4. The ufe of the large apparent artery fpread on the cotyledons 

 of a germinating feed of a garden-bean, called feminal roots by Grew, 

 as (hewn in Plate I. Fig. i, and that fpread on the chorion of the 



I 



chick in the egg, fo called by Malpighi, and fhewn in Tom. II. Fig. 



54 



and 



Fabricius ab Aquapendente, Tab. I. 



Fig. 



I 



3, which 



* 



inuft be an artery, as it carries red blood, are believed to be refpiratory 

 organs, like the placental vefTels of the fetus of viviparous animals, 

 becaufe the cotyledons of fome feeds rife out of the ground, and be- 

 come leaves, after the nutriment they contained is expended, and 

 are then called feminal leaves, as in the kidney-bean, phafeolus ; and 

 becaufe thofe which do not rife out of the ground perifli beneath the 



foil, as foon as the young plant gains its leaves, which are its aerial 

 refpiratory organ. 



Secondly, the chorion of the chick confifts of a membrane includ- 

 ing the white, or albumen, and is not only in contact with the air- 

 as the chick advances, co- 

 vers more than half of the internal furface of the (hell, but alfo with 



h 



the membrane which lines all the other part of the fhell, as appears 

 in Plate III. which is copied from Malpighi: yet this 'extenfive 

 chorion, with the numerous arteries and veins which are fpread upon 

 its furface, is not drawn up into the body of the chick like the yolk 

 and its including membrane, but perifhes at the nativity of the chick 



bag at the broad end of the egg, which. 



like the placental vefTels of the fetus of viviparous animals ; or fome- 



times 



' 



\ 



> 



