284 IMMUNOLOG1CAL METHODS OF DIAGNOSIS 



capable of giving rise to precipitin formation, when injected into 

 animals of an alien species, Uhlenhuth especially drew attention 

 to the remarkable specificity of the reaction when applied to the 

 study of the blood of different animals. He thus laid the foundation 

 of the modern biological blood test which is now recognized as 

 proper evidence regarding the origin of blood stains, in the courts 

 of practically all civilized countries. 



Aside from these more practical bearings the precipitin reaction 

 has attracted a great deal of attention owing to the unexpected 

 light which it has thrown upon the biological relationship existing 

 between different animals. For it has been shown that while the 

 precipitins which can be produced in a rabbit, for example, by the 

 injection of the serum of a horse and which naturally will react 

 with the latter, likewise do so with the serum of the donkey and 

 the tapir. An antidog serum will similarly react with the serum of 

 the fox, antichicken serum with pigeon serum, antigoat serum with 

 sheep and bovine serum, antihuman serum with the serum of 

 apes, etc. 



These group reactions are readily explained if we assume the 

 existence in the antigenic sera of "partial" precipitinogens, i. e., of 

 precipitinogenic molecular complexes which are peculiar to a special 

 species, besides others which are common to a whole group of 

 species, all of which will naturally give rise to corresponding "partial" 

 precipitins, in a manner quite analogous to the formation of 

 "partial" agglutinins (which see). That such partial precipitins 

 actually exist in an antiserum may be shown by treating antihuman 

 serum with monkey serum when the antimonkey precipitin will cause 

 the formation of a corresponding precipitate. If this is then removed 

 by centrifugation (quantitative relations being, of course, duly 

 considered) the remaining serum may be shown to have retained 

 its precipitin for human serum, while that for monkey serum has 

 disappeared. That antihuman serum, moreover, should possess a 

 larger quantity of antihuman than of antimonkey precipitin would 

 naturally suggest itself and can be demonstrated by suitable methods. 



The technique which is involved in these various examinations 

 may be suitably described in connection with its application to the 

 medico-legal blood test, according to Uhlenhuth. 



The Biological Blood Test. As the legal question at issue is 

 usually whether or not a certain blood stain is of human origin, it 



