166 Tests with Precipitins 



and ape bloods. This great reaction with the blood of the two 

 Cercopithecidae appears to find its explanation in the cause of death 

 which was given for these two animals (Nos. 49 and 58) viz., intus- 

 susception and dysentery. In both of these affections the blood 

 is liable to become concentrated, and therefore, taken volume for 

 volume, the serum of such an animal will contain more of the 

 reacting body than does normal serum. Within limits, moreover, the 

 more concentrated a blood dilution, the more precipitum will it yield 

 upon the addition of an antiserum. In point of fact then, the bloods of 

 Cercopithecidae give under ordinary conditions a very moderate reaction 

 as compared to those of Hominidae and Simiidae. Three negative 

 results amongst the Cercopithecidae (Nos. 49, 59, 75) are due to some 

 common cause, which I am not at present able to fully explain. All 

 three bloods were sent to me by Dr Langmann from the New York 

 Zoological Gardens. None of them went well into solution, a fact which 

 was possibly due to their having been exposed too long in the sun, or 

 affected in some other way. The bloods of the Cebidae and Hapalidae 

 show a still further reduction in the amount of reaction. 



If we include even the faint and medium cloudings ( * x) 

 amongst the positive reactions, we see that the percentage 'of positive 

 reactions falls as we read doivn the column of the reactions with the 

 bloods of Primates, from man to the Hapalidae. It must however not 

 be lost sight of, that the great reactions in the two last columns are 

 those which more clearly show the relationship. When we come to 

 consider the other Mammalia, we see that there is a notable absence 

 of larger reactions, the largest reactions noted being a few medium 

 cloudings, and these occurred most frequently amongst the Carnivora 

 and Ungulata. This will be better seen by reference to the percentages 

 bracketed alongside the figures. The percentage of faint and medium 

 cloudings in all the mammalian bloods examined, outside the Primates, 

 amounts but to about a half of that noted for the Hapalidae, viz. 24/ . 

 Amongst the Primates we see that the result of the test with two 

 lemurs was negative. I demonstrated a small series of primate bloods 

 before the Royal Society (21 Nov. 1901), which showed this progressive 

 decrease of reactions from the Hominidae downward, and no reaction 

 with the lemur bloods. I stated at the time, that a weaker antiserum 

 included the Hominidae, Simiidae and Cercopithecidae within its 

 sphere of action. When the antiserum was stronger it included the 

 Cebidae and Hapalidae, these reactions being comparatively very slight. 

 On the other hand, if we use a very powerful anti-human serum, faint 



