Page:George Archdall Reid 1896 The present evolution of man.djvu/253

Rh when attacking races that they have little or not at all afflicted. Judging by current literature, this difference of type is generally regarded as something altogether inexplicable, or sometimes it has been said that this or that race has become acclimatized to this or that disease, when the common and very foolish error has been made of imagining that a phenomenon named is a phenomenon explained. To say that a race has become acclimatized to a disease—i.e. that it has become more resistant to it—does not explain how that increase of resisting power arose. When in rare cases an attempt has been made to probe deeper, it has generally been on lines of the Lamarkian doctrine of the transmissibility of acquired traits ; and as often as not it has been made by thinkers who possibly never heard of Lamark, and who would repudiate the logical outcome of their own arguments—the idea of evolution. Starting with the fact, that in many zymotic diseases one attack confers immunity against subsequent attacks, it has been tacitly assumed, if not expressly asserted, that this acquired immunity, or some of it, is transmitted from parent to child, each successive individual of the line beginning life with more resisting power than his parent began with, and transmitting more to his offspring than he received. But besides the general considerations which lead us to deny the transmissibility of