146 PROPERTIES OF ANTI-SERUM TO SERUM 



as in the deviation experiments, and then in the refrigerator 

 till next morning, when the results are read off. With 

 0-05 c.c. of our anti-serum rabbit v. ox a distinct precipitate 

 is got on the addition of 0-001 c.c. of ox's serum, a very faint 

 precipitate with 0-000, 1 c.c., this latter being scarcely reliable 

 for practical purposes. Distinct deviation of rabbit's and 

 guinea-pig's complement is got with 0-000,01 c.c. of ox's 

 serum and appreciable deviation sometimes even with 

 0-000,001 c.c. With the serum rabbit v. man 0-05 c.c. pre- 

 cipitation is distinct with 0-001 c.c. of human serum, almost 

 absent with 0-000,1 c.c. ; deviation of complement is always 

 got with 0-000,01 c.c. We may thus state that in the case 

 of these two sera the deviation test is between ten and 

 a hundred times more delicate than the precipitin test. 

 Neisser and Sachs in the case of an anti-human serum con- 

 sidered that the deviation test was about forty times more 

 delicate, and Friedberger found an even greater difference 

 between the two. The figures which we have stated may 

 be taken as well within the limits, as we have taken the 

 smallest amount of serum which gives a distinct deviation. 

 Furthermore, owing to the nature of the reaction the result 

 is much more easily appreciated than in .the case of pre- 

 cipitins, especially when there is any natural cloudiness of 

 the serum. 



We have also found that the phenomenon of deviation 

 may be well marked in the case of an anti-serum which gives 

 no precipitate. Nuttall states that when the animal used 

 for injection is of closely allied species to that from which 

 the serum is taken a precipitin is not usually developed. 

 We have obtained a result which confirms this in the case 

 of the anti-serum rabbit v. guinea-pig. This anti-serum 

 produces no distinct precipitate even when a comparatively 

 large amount e.g. 0-01 c.c. of the homologous serum is 

 added ; at the most there is only some opalescence, and if 

 the tubes be allowed to stand for twenty-four hours there 



