720 NITROGEN METABOLISM AND GROWTH 9 



convincing evidence of differential permeability of the membrane to the various 

 kinds of protein involved". Examination of the blastocyst fluid showed albumen, 

 a-, [3- and y-globulins in approximately the same proportions as in adult plasma. 

 It was demonstrated that antibodies to Brucella abortus passed from the mother 

 to the yolk sac cavity (Brambell, Hemmings and Rowlands, 1948), and further 

 (Brambell et al., 1949) that ''the allanto-chorionic placenta is an effective barrier 

 to the passage of agglutinins in many, and probably in all, embryos". The 

 absorption through the omphalomesenteric circulation and passage thence into 

 the yolk sac cavity, they suggest, offers an experimental means of testing the 

 introduction of proteins into the embryonic circulation without interfering with 

 the maternal circulation. Brambell, Hemmings and Henderson (1951) have 

 summarized their own as well as other pertinent studies and discussed the 

 implications of the work. 



Ranzi (1951) describes the presence of fibrillar proteins (euglobulin a and b), 

 a globular protein (euglobulin c) and a pseudoglobulin, having a folded fibrillar 

 shape, in the eggs of sea urchins, fowl and frog eggs. The similarity of form of 

 protein molecules in the three diverse forms is of interest, but of more pertinence 

 is the identity of at least certain of the yolk proteins with those of the mother. 



The serological similarity between proteins of the egg and serum seems well 

 established (Schechtman, 1947; Nace and Schechtman, 1948; Schechtman and 

 Hoffman, 1952). 



Nace (1953) found that livetin of yolk contains components representing each 

 of the adult serum fractions and that each adult serum fraction contains yolk-like 

 constituents. Antigenic determinants resembling those of serum albumin can be 

 detected on or before the fifth day, those of a and ^-globulins about the sixth day 

 and those of y-globulin between the ninth and twelfth day. "Just prior to the 

 appearance of these constituents a vitelloid (yolk-like) antigen resembling each 

 of them can be detected. It is suggested that the protein of the yolk forms a source 

 of serum protein available to the embryo until its own synthetic mechanism is 

 established, and secondly that such protein, originally derived intact from the 

 maternal organism, may provide models (templates) for serum protein synthesis 

 by the embryo." Independently Ranzi (1951) identified at 6 days the appearance 

 of a globular protein soluble in o.i M KCl and after the 9th day a large synthesis 

 of fibrillar or folded fibrillar proteins. These may be the same elements identified 

 serologically by Nace (1953). Clayton (1953) studied the same phenomenon in 

 the newt and observed that "some adult antigens may be found as early as in the 

 fertilized egg, and some of these may have been directly derived from the inaternal 

 organism". 



Cooper (1946) found some evidence for identity of antigens of the egg, embryo 

 and adult serum of Rana pipiens. Earlier literature (reviewed by Cooper) appeared 

 to be negative or conflicting in this regard; the difficulties, she feels, were tech- 

 nical. When the technique of absorption by adult serum was used, saline extracts 

 of developmental stages "failed to react or had lower titres in ring tests with 

 anti-frog brain sera absorbed with frog serum than with anti-frog brain sera 

 correspondingly diluted but unabsorbed". In a later paper (1948) Cooper is 

 more positive: "eggs and young embryos certainly contain molecules capable of 



