On the Inheritance of the Mental Characters in Man. 153 



Hapalidse, 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. 



Referring to the anti-serum for human blood, I may state that I 

 have successfully produced it in rabbits by injections of old human 

 pleuritic exudate preserved in a bottle with chloroform for five to six 

 months. Similarly, some old anti-diphtheritic horse serum preserved for 

 two years and seven months in the laboratory by means of trikresol 

 also yielded an anti-serum for horse blood. The anti-sera produced in 

 these cases was feebler than that which is produced by injections of 

 fresh serum. Dilutions of these old preserved fluids gave the charac- 

 teristic reactions with their homologous anti-sera. I have also found 

 that the anti-sera may be preserved for months with chloroform, 

 although there is no denying that they lose in power. Anti-serum 

 which had been preserved for over seven months in sealed capillary 

 tubes was likewise still effective, although less potent. 



Through the kindness of Mr. Frank E. Beddard, F.R.S., Prosector 

 of the Zoological Society's Gardens, and numerous friends, who are 

 generously aiding me by sending blood-samples from various parts of 

 the world, I am gradually gathering together considerable material 

 for study. Wherever possible the fluid sera are being sent me pre- 

 served with chloroform. Dried sera, on the other hand, are sent on 

 slips of pure filter-paper, upon which appropriate data are noted in 

 pencil. 



The results of the investigation indicate the necessity of not limiting 

 the work to vertebrates alone, and many questions naturally suggest 

 themselves, the solution of which may be attained by means of the 

 biological test. 



The assumption seems justified that we may, for instance, be able at 

 some future date to determine chemical differences in the blood of the 

 various races of man. We no longer need to rely solely upon morpho- 

 logical characters for the differentiation of species. 



It is impossible to enter into details concerning the nature of the 

 reaction here described ; it is a subject for further study. Suffice it 

 to say that it is exceedingly complex, but at the same time the most 

 delicate of tests known. 



" On the Inheritance of the Mental Characters in Man." By 

 KARL PEARSON, F.R.S., University College, London. Received 

 November, 2, Read November 21, 1901. 



(1.) Mr. Francis Galton, in his ' Natural Inheritance,' first, I 

 believe, endeavoured to give a quantitative appreciation of the 

 inheritance of the mental characters in man. Mr. Galton's data 



