The influence of contagions and infections on degeneracy is therefore by no means slight. Each disease can produce grave constitutional defects in the ancestor likely to be intensified in the offspring. The greatest social dangers result from tuberculosis; the next from syphilis. Typhoid fever, scarlatina, small-pox, measles, diphtheria, whooping-cough, and all other contagions, however, may produce these constitutional defects, either through the mother during pregnancy or through their secondary effects on the ancestor's constitution. If the subject be attacked before the close of the periods of dental stress an arrest of development of the bones of the face may result with irregularities in the shape and position of the teeth. These, then, are stigmata of degeneracy, especially due, in the individual presenting them, to the contagions and infections rather than to inheritance alone. CHAPTER VIII CLIMATE, SOIL, AND FOOD Among the factors constituting environment few have impressed the biologist so much as climate, soil, and food. The seeming modifications produced by these have made a very decided impression on the sceptical Weismann, who stated that "the possibility is not to be rejected that influences continued for a long time, that is, for generations, such as temperature, climate, kind of nourishment, &c., which may affect the germ plasm, as well as any other part of the organism, may produce a change in the constitution of the germ plasm. But such influences would not then produce individual variations, but would necessarily modify, in the same way, all the individuals of a species living in a certain district. It is possible, though it cannot be proved, that many climatic varieties have arisen in this manner. Possibly other phenomena of variation must be referred to a variation in the structure of the germ plasm produced directly by external influences." Considering the changes brought about in European plants and animals in Australia, those occurring in the East Indian mongoose in Jamaica, the changes in European plants and animals in America, or American animals in Europe and European animals in Asia, Weismann's position seems judicial. The influences dependent on food, soil, and climate producing normal modifications have been remarkably illustrated in the gilled batrachian Axolotl. This, under the nourishment and change of surroundings of the Jardin des Plantes, was transformed into a gill-less batrachian, which had hitherto been regarded as belonging to a totally distinct family.