allantois, tallantoid

[In Fr. and Port, all an to ide; from Gr. ἀλλαντοειδής ( all an toe ides ) = shaped like an ἀλλᾶς (all as), gen it. ἀλλᾶντος ( allantos ) = a kind of meat, intermediate between our sausage and black pudding.] A thin membrane existing in the embryos of amniotic vertebrata. It is situated under the chorion, and outside the amnion of the embryo. It is well developed in the Ruminant i a, but le so in the Rodent i a. In the chick of birds it becomes applied to the membrane of the egg-shell, and constitutes the breathing apparatus of the young animal till the lungs are formed. The embryo of man po e es an allantois, which, however, is but transient, shrivelling before the end of the second month of development, and soon afterwards entirely disappearing. ( Todd & Bowman: Physiol. Anat ., vol. ii., pp. 590, 603, 620.) al-lan-tür-ic, a. [Eng. allantois; uric.] Obtained from allantoin and uric acid.