ABSTRACT
Many permanent variations brought about by causes producing disease, that is to say, many diseases, are nothing but dangerous adaptations of the organism to injurious conditions of life. Speaking quite generally, indirect or potential adaptation consists in the fact that certain changes in the organism, effected by the influence of nutrition and of the external conditions of existence in general, show themselves not in the individual form of the respective organism, but in that of its descendants. Some naturalists, especially Charles Darwin, Carl Vogt, and August Weismann, ascribe to the indirect or potential adaptation by far the more important and almost exclusive influence. The principal and most universal of the laws of indirect variation may be termed the law of individual adaptation, or the important proposition that all organic individuals from the commencement of their individual existence are unequal, although often very much alike.
