560 



Ontogeny of Immunological Properties 



gens. The various experiments seem to be 

 in accord in that the younger the embryo the 

 less organ antigen is detectable, as illustrated 

 in Table 23. It is, however, clear that the 

 complete absence of an antigen cannot be 

 proved by serological methods. So the pos- 

 sibility remains open that "adult" antigens 



therefore, absorbed with frog serum. When 

 the absorbed antisera were tested with the 

 saline extracts of brain, liver, kidney and 

 heart, their precipitin titers (dilution of 

 antigen) were found to be greatly reduced. 

 It could be concluded, then, that the presence 

 of serum or of tissue substance with "serum- 



Table 22. Reactions of Brain- and Lens-Antisera with Saline Extracts of Brain and of Lens, 

 Respectively, of Chick Embryos of Vari.Ms Ages (after Burke et al., '44) 



Table 23. Precipitin Reaction of Adult Lens Antiserum with Saline Extracts of Embry- 

 onic Chick Lens {after Ten Cate and Van Doorenmaalen, '50) 



Age of embryo, hours 192 



Last reactive dilution of extract .... 6400 



54 



may be present in the earliest stages of 

 development, or even in the unfertilized egg. 

 Cooper ('46) demonstrated that antisera 

 against saline extracts of the brain of adult 

 frogs react with extracts of the eggs, embryos 

 and larvae and of adult liver, kidney, heart 

 and serum. Although the brain extract used 

 for immunization, as well as the other organ 

 extracts used in the tests, had been well 

 washed it was suspected that serum might be 

 present in these and be responsible for the 

 cross-reactions. The anti-frog-brain sera were, 



like" determinants largely accounted for the 

 cross-reactions. Since some reactivity for the 

 organ extracts remained after the absorption, 

 this indicated that there may also be anti- 

 gens other than those with serum-protein 

 determinants that are common to brain and 

 the other organs tested. When the absorbed 

 antisera were tested with saline extracts of 

 the eggs, embryos and larvae the titers were 

 also found to be greatly reduced, as is illus- 

 trated in Table 24. These results again show 

 that antigens with serum specificity are 



