Blood Relationship 137 



interval of time had been able to settle. I have observed such deposits 

 when antisera were not clear, although not of the opalescent kind (see 

 p. 72). That even rabbit blood gave a precipitum indicates possible 

 errors in his technique. 



Uhlenhuth (25, viz. 1901) agrees with me in finding that the 

 zoological relationships between animals are best demonstrated by means 

 of powerful antisera. He judged from reactions with such antisera, 

 that the ox is not so closely allied to the sheep, as the sheep is to the 

 goat. He found that weak anti-sheep serum produced no reaction 

 in ox blood. In my paper of 21, xi. 1901, 1 wrote "The more powerful 

 the antiserum obtained the greater is its sphere of action upon the bloods 

 of related species. For instance, a weak anti-human serum 1 produced 

 no reaction with the blood of the Hapalidae, whereas a powerful anti- 

 serum did produce a reaction, and proved what I may be permitted 

 to call the ' blood relationship ' in the absence of a better expression." 

 This generalization was based upon data, previously published, with 

 regard to the general action apparently possessed by anti-ungulate sera 

 upon certain ungulate bloods (see anti-ox and anti-sheep blood tests, etc.), 

 as well as on the bloods of Canidae and Primates. I also noted that 

 reactions took place "to a lesser extent, in the bloods of allied animals, 

 than in the homologous blood 2 ." This was of paramount importance, 

 the statement being based upon the examination, not of one or two 

 bloods, but of over 200. In a subsequent paper (16, XII. 1901, p. 408) 

 speaking of the reactions amongst the Primates, I wrote "If we accept 

 the degree of blood reaction as an index of the degree of blood-relationship 

 within the Anthropoidea, then we find that the Old World apes are 

 more closely allied to man than are the New World apes, and this is 

 exactly in accordance with the opinion expressed by Darwin." I cite 

 these earlier papers for the reason that I wish to make it clear that 

 my results have materially contributed to a modification of the views 

 held with regard to the specificity of these reactions. 



I have already shown that a reaction may take place with even the 

 distantly related blood of the horse, very slight it is true, upon the 

 addition of anti-human serum. This was confirmed by Griinbaum 

 (18, 1. 1902, p. 143) working with another anti-primate serum, that for the 



1 When a powerful antiserum is diluted, corresponding results may be obtained. See 

 pp. 74 and 142. 



a Exceptions, notably in the case of ungulate blood (q. v.) have since been noted by 

 me and are recorded in this book. They may however be due to the effects of disease on 

 the animals yielding the blood tested. 



