 “Blood poisoning”! The worry here is about the Jews and their supposed ill-effects on pure races. The Jews do not get a mention in the Descent of Man (1871), and although Darwin supposes that white races tend to wipe out others, it is not from any mental or physical superiority, but because we can tolerate their diseases but they cannot tolerate ours! And this is all because whites have had a bigger pool of variants to draw on than have others. 