PRECIPITIN REACTIONS 321 



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 

 medicolegal 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 is ordi- 

 narily only necessary to examine the material in question in reference 

 to its behavior toward an antihuman serum. If, on the other hand, 

 the antihuman investigation has shown that the material was not 

 of human origin, and it is desired to ascertain from what animal 

 species the blood was derived, corresponding sera must, of course, 

 also be available. 



PREPARATION OF THE ANTISERA. The antisera in question are 

 usually obtained from rabbits after injection with either human 

 serum, pig serum, or bovine serum, etc., as the case may be. The 

 injections are given intraperitoneally or intravenuosly at intervals 

 of five or six days, using 10, 8, and 5 c.c. respectively in the first 

 instance, and 5, 3, and 2 c.c. if the latter method is preferred. It is 

 always best to inject several rabbits at the same time, especially 

 since not every animal furnishes a serum with a sufficiently high 

 titer. According to Uhlenhuth this should be such that 0.1 c.c. 

 of the antiserum shall produce a distinct turbidity either instan- 

 taneously or at most after one to two minutes* when added to 1 c.c. 

 of a 1 to 1000 dilution of the corresponding antigenic serum. Added 

 to 1 c.c. of a 1 to 10,000 and 1 to 20,000 dilution a turbidity should 

 be discernible after three and five minutes respectively, while a 

 control specimen, containing only 0.85 per cent, saline (the diluent 

 in question) and 0.1 c.c. of the antiserum must, of course, remain 

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