DEVELOPMENT OF THE CHICK. 213 



circulation into the membranes for the influence of air, which membranes 

 may be called the foetal lungs. 



The vessels of the chick are different from the human, more like [those 

 of] the pnppy or kitten, although different from them in some of their 

 vessels. The motion of the blood in the chick, in and through the heart, 

 is not different from [that in] the quadruped ; that is, the communica- 

 tion between the right side and the left is the same, having a foramen 

 ovale, but the communication between the two arteries is a little 

 different, having two ' canales arteriosi' instead of one. 



Of the peculiar Arteries of the Chick. 



These arteries are three ; the two first, or what may be called a pair, 

 and which answer to the umbilical arteries in the quadruped, arise 

 from the iliacs, and pass by the sides of the bones of the pelvis towards 

 the opening of the abdomen, and when got out of that cavity through 

 this opening, ramify on the three membranes above described. The 

 third 1 is a continuation of the mesenteric artery, and is principally lost 

 on the membrana lutei. 



Of the Veins. 



There are two venae umbilicales ; one (which is the largest) belongs 

 to the amnios, chorion and lungs 2 , and is similar in its termination to 

 the umbilical vein in the quadruped, the trunk of which passes into 

 the abdomen, then upwards to the liver, enters between its lobes, and 

 opens into the vena cava inferior, just as it enters the heart. The other 3 

 belongs to the membrana lutei, and passes into the abdomen, joins the 

 mesenteric vein, which would appear to divide into two, one forming 

 the vena portarum, the other joins the vena cava inferior between the 

 kidneys, and which communication remains through life. 



In the diastole of the auricles more blood passes into the right than 

 what it can contain, and the overplus passes, as it were, through the 

 right auricle into the left, while at the same time the left is receiving- 

 blood from the lungs, so that the left is filled partly from the body, 

 therefore they are equally filled with blood. But the quantity from 

 the lungs is increasing every day in proportion as the lungs increase, 

 for the lungs can hardly be said to be coeval with the heart. 



1 [Vitelline or omphalomesenteric artery.] 



2 [By ' chorion and lungs' Hunter intends the ' allantois.'] 



3 [Vitelline or omphalo-mesenteric vein.] 



