In a later article[182] Steinach published results of experiments upon the exchange of sex glands in other animals between the different sexes and found that the female masculated by being given the testes of her brother followed more or less his development rather than her own, almost equaling him in growth, weight, and robustness. This Steinach calls hyper-masculinization and a degree of this follows the development of the glands after transplantation, which the microscope showed was attended by real intussusception. He also showed hyper-feminization, so that we have a change of the ovaries into hypertrophic but analogous pubertal glands, with corresponding change of traits, dependent upon the degree of success or completeness of the operation. Thus he thinks, too, we can explain somatic and psychic precocity by the hypertrophy of these glands. In another article[183] the author emphasizes the great variability in the development of sex, both as to size of organs and their functions in different individuals and believes that besides environment, heredity, race, etc., climate has a great deal to do with it. He finds that in warm countries the advent of sex maturity is somewhat earlier in all its aspects, although there is some suggestion that these accelerations may be connected with the development of other secondary traits. Experiments made with animals in artificial climates point to the same result and changes in this direction are observed in animals accustomed to cold that are transported to warm climates. Interesting as these experiments on the interchange of primary and secondary sexual qualities are, they were, for Steinach, only preliminary to what chiefly concerns us here, namely, his studies of rejuvenation[184] and his problem was to see whether by his operations he could shed light upon the problem of whether age is a condition we are defenseless against, like an incurable disease, or senescence can, at least within certain modest limits, be influenced. He says his experiments have decided in favor of the latter alternative. He had first to determine whether orthoplastic, homoplastic, or a combination of both methods was the best. The former was chosen because it was quickest and easiest and independent of earlier implantation material, especially with men. And so, with his colleague, Lichtenstern, various operations were performed, of which three type cases are as follows: