ORGAN (TISSUE) DIFFERENTIALS 541 



specificity. This interpretation agrees with the findings of v. Szily, to which 

 we shall soon refer. 



However, that organismal differentials are still present in the lens is also 

 indicated by the fact that injection of homoiogenous lens material in the 

 rabbit does not, as a rule, lead to the production of antisera, but it is neces- 

 sary for this purpose to use heterogenous lens substance, and conversely, in 

 a rabbit sensitized with strange lens material its own lens cannot call forth 

 an anaphylactic reaction. This observation is in agreement with the demon- 

 stration of individuality differentials in lens tissue by means of cellular 

 reactions. Still, according to Guyer, it seems that a guinea pig can be 

 sensitized to strange lens material by injuring the animal's own lens. It is 

 possible that in the case of the lens a very pronounced organ specificity 

 covers up the more finely graded organismal differentials and allows only 

 the very coarse ones to become manifest. In agreement with this interpre- 

 tation would be the experiments of Defalco, who obtained species-specific 

 precipitins for the avian lens. 



6. Two different types of organ-specific constituents have been demon- 

 strated in the brain by Witebsky and his collaborators. Witebsky and 

 Steinfeld showed that there are (1) alcohol soluble, coctostable substances. 

 The antigen, or rather hapten, present in an alcohol extract from the brain 

 of a given mammalian species, reacts not only with the immune serum 

 produced against the brain extract from this particular species, but also with 

 those of all other mammalian species. It is therefore to a very high degree 

 organ-specific, and to a much lower degree, or not at all, species-specific. 

 Similar organ-specific, alcohol soluble differentials can be shown to exist in 

 the posterior lobe of the hypophysis and in the medulla of the adrenal gland. 

 (2) In addition, there are demonstrable in brain suspensions, heat-sensitive 

 substances, which are not soluble in alcohol and which react only with the 

 immune serum against the brain of the species from which this organ was 

 derived; hence, beef brain suspensions react only with immune serum 

 against non-heated beef brain suspensions. These differentials, which are 

 presumably of a protein nature, are therefore not only organ-specific, but 

 also, to a high degree, species-specific. The immune serum prepared against 

 non-heated brain suspensions reacted in some instances also with alcohol 

 soluble antigens; but such a reaction did not take place if the corresponding 

 immune serum against certain other organs, such as the epiphysis, were tested 

 in a similar manner. 



While in some cases, according to Witebsky and Lehmann-Facius, boiled 

 or alcohol soluble organ extracts seem to be better suited than watery, non- 

 heated extracts for the demonstration of organ-specific constituents, this 

 apparently is not true in all cases. Thus it is possible to distinguish by means 

 of complement fixation between brain and epiphysis, if we use immune sera 

 prepared against the unheated, water soluble antigens; but immune sera 

 against the heat stable, alcohol soluble substances in epiphysis and brain do 

 not make possible the distinction between these two organs. The alcohol 

 soluble substances in brain and epiphysis are evidently identical, or at least 



