ORGAN (TISSUE) DIFFERENTIALS 535 



specificity of the lens of the eye ; from the lens substance, partial antigens, two 

 crystallins, may be separated, and also against these specific precipitins can 

 be produced, which are the same irrespective of the species from which the 

 antigens are derived (Hektoen and Schulhof ) ; this is an observation which 

 is in accordance with what has been found in the case of the precipitins 

 against the lens as a whole. However, these two crystallins are related to each 

 other, because cross-immune reactions between them do occur. We see, then, 

 that in this instance the organ specificity can be reduced to the specificity of 

 certain substances derived from these organs. But in a preceding chapter we 

 have seen that according to Defalco it is possible, by means of the precipitin 

 reaction, to demonstrate in the lens of birds the presence of species 

 differentials. 



The brain behaves in a similar manner to the lens ; it also shows a very 

 pronounced organ specificity, which may or may not be associated with 

 species specificity. However, as stated, immune serum against brain reacts 

 equally well with testis (J. H. Lewis). Also, vitellin obtained from egg yolk, 

 as well as casein and thyreoglobulin (Hektoen) are organ- or rather 

 substance-specific material. Anti-thyreoglobulin sera do not react with 

 globulins from other organs. 



In other cases a more graded specificity exists. Thus immune serum 

 against egg albumin reacts also with albumin from fowl serum ; yet both 

 these albumins can be distinguished by means of quantitative tests. Fibrinogen 

 and the globulins of chicken plasma are immunologically nearly related to 

 each other; but they can be distinguished by means of quantitative tests with 

 immune sera; they are very different from the albumins of fowl's egg or 

 fowl serum. Similar relationships are found between serum globulins of 

 mammalian organisms (Hektoen and Welker). As Dale and Hartley, as 

 well as Doerr and Berger, have shown, the serum proteins exhibit two kinds 

 of specificities: (a) The species-specificity, which depends upon the char- 

 acter of the organismal differentials ; this is the same in the various plasma 

 proteins from the same blood, (b) The fraction-specificity, so-called by 

 Doerr, which corresponds to organ-specificity. Each mammalian serum protein 

 can be distinguished from another serum protein derived from the same 

 individual or species by means of the anaphylactic reaction. Likewise, Bence- 

 Jones protein, which occurs in the urine under certain pathological conditions 

 (multiple myeloma), is serologically quite different from the normal serum 

 or plasma proteins. Immune sera against hemoglobin react with hemoglobin 

 but not with serum proteins. Furthermore, the antihemoglobin sera are quite 

 distinct in their reactions from immune sera against the stroma of erythro- 

 cytes ; the latter contain hemolysin and hemagglutinin, in contrast to the anti- 

 hemoglobin sera, which do not contain these two antibodies. In general, the 

 organ proteins are distinct from the proteins of the bodyfluids, although the 

 latter may be derived from certain organs. On the other hand, we have men- 

 tioned the close relation which exists between albumin from egg and from 

 serum. 



In lens and brain, lipoid substances seem to be at least partly responsible 



