THE POSITION OF THE RESPIRATORY VASCULAR 

 NET IN THE ALLANTOIS OF THE CHICK 



VERA DANCHAKOFF 



From the Anatomical Laboratory of Columbia Universily 



ONE PLATE 



The structure and function of some of our organs seems to be 

 so well established, that it requires a certain courage to com- 

 municate new observations in fields which seemed to be ex- 

 haustively studied. My observations refer to the arrangement 

 of the respiratory capillary net in the allantois of the chick. 



In the chick embryo from the sixth day of incubation until 

 hatching, the capillaries of the allantois subserve the function 

 of respiration. 'The allantois is a sac, the walls of which are 

 flattened by the narrow space offered to its development and can 

 be considered as two sheets. The outer sheet contains the richly 

 developed respiratory net, which, according to Fiillborn's^ ex- 

 pression, can be compared with a sinus traversed by trabeculae 

 of mesodermal tissue. 



The respiratory capillaries of the outer sheet of the allantois 

 are homologous in their function, according to Schulte's termi- 

 nology homodynamous, to the respiratory capillaries in the pla- 

 centa of the mammalian embryos and to those of the lungs and 

 the gills in the definitive respiratory organs of vertebrates. The 

 respiratory capillary net manifests in its structure as well as in 

 its relation to the constituent parts of the organs, in which they 

 develop, perfectly similar features. No where seem the respira- 

 tory capillaries to come into immediate contact with the air or 

 with the fluid, which contains the oxygen. The endothelial 

 wall of the capillaries is separated from the immediate action of 



' Fried. Fiillborn, Beitrage zur Entwicklung der Allantois der Vogel. Inau- 

 gural Dissertation. Berlin, 1895. 



407 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 21, NO. 3 



