ALLANTOIS

(Yunanca köken — orijinale bakınız.) A thin membranous sac developed from the termination of the alimentary canal of the embryo, situated between the amnion and chorion, and organised by the hj'pogastric arteries and umbilical vein. Its function, as a temporary respiratory organ, is of most importance in those oviparous vertebrates where the embryo has no branchiae; in the mammal i a, its use is more or le superseded by the chorion and placenta. In some quadrupeds the ailanto is has the form of a sausage; whence its name. [s. 45]