Note that classes are here required in extension, so that the class of human beings and the class of rational featherless bipeds are identical; similarly for relations, which are to be determined by the entities related.
It has been held that animal sacrifice is the primitive form and that the decay of totemism or lack of domestic animals has brought about the substitution of a human victim; but it has also been urged that in many cases animal victims are treated like human beings and must consequently have replaced them, that human beings are smeared with the blood of sacrifice, and must therefore have themselves been sacrificed before a milder regime allowed an animal to replace them.
The waters of these two lakes are only moderately saline and may be used for live-stock but not for human beings.
It was, however, one thing to experiment on dogs, and quite another to do so on human beings.
He also believes that human beings may infect rats.