. The American journal of anatomy. continuation of the postcava,and a renal portal system isestablished on the right after this, however, ananastomosis takes place be-tween the two subcardinalsventral to the aorta and caudalto the A. omphalomesenterica,and by this means the bloodfrom the left subcardinal alsopasses into the postcava. Thisbrings about a complete renalportal system. The anasto-mosis between the two subcar-dinals marks the future bifur-cation of the adult the mesonephroi enlargeand occupy a considerable por-tion of the body cavity theygrow around the subcard
. The American journal of anatomy. continuation of the postcava,and a renal portal system isestablished on the right after this, however, ananastomosis takes place be-tween the two subcardinalsventral to the aorta and caudalto the A. omphalomesenterica,and by this means the bloodfrom the left subcardinal alsopasses into the postcava. Thisbrings about a complete renalportal system. The anasto-mosis between the two subcar-dinals marks the future bifur-cation of the adult the mesonephroi enlargeand occupy a considerable por-tion of the body cavity theygrow around the subcardinals,wliicli thus become enclosedwithin their median side andare carried somewhat brings about a closer rela-tion between the mesonephroiand the subcardinal consequence of this closerrelation the latter vessels in-crease in size and receive bloodfrom the mesonephroi throughlarge branches, as indicated in Fig. 6 (a) (chick of 5 days incubation)With the increased amount of blood from the mesonephroi and the en. Fig. 5. Reconstruction of the venous system ofa chick of 90 hours. Ventral view. X 50. {Expla-nation of lettering on page 284.) 290 The Development of the Postcaval Vein in Birds largement of the snbcardinal veins the stem of the postcava attains cor-responding i)ro|)ortions. At the end of tlic r)th day of incubation thesnbcardinal system has reached its lieight of development, and at thisstage is seen the immense importance of the snbcardinal veins in thedevelopment of the postcava. They form the entire efferent system,and moreover a great quantity of blood passes through the renal portalsystem, for the anterior ends of the postcardinals by this time have be-come much diminished in size and are unable to carry a very large pro-portion of the blood to the duct of Cuvicr. The significance of these snbcardinal veins in birds is even betterappreciated by a glance at the conditions found in adult reptiles, wherethe efferent veins of the renal port
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
