The invalidity of the sale and the purchase of blood and...

The invalidity of the sale and the purchase of blood and human excreta is only an instance of the application of that principle. Even where no exchange is involved, money or property belonging to someone else cannot be appropriated and disposed of gratuitously. The law forbidding the appropriation of another’s property gratuitously is a firm principle that is applicable to all time, and has emerged from a permanent social need.

But, the rule that blood and excreta are not to be regarded as wealth and are not saleable is related to time and the degree of civilization. This rule is subject to modification with the change of conditions, the progress of science and industry, and…