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.
(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
