As we have shown in our previous researches, there is an abundant formation of fat in the early cases of degeneration of the thyroid gland, which sometimes progresses to a colossal obesity, which obesity has nothing to do with overfeeding. Such individuals have, as a rule, but poor appetites, and eat very little. Therefore, in a communication to the French Congress of Internal Medicine in Paris, 1904, we differentiated two kinds of obesity: 1. _Exogenous obesity_—i.e., arising by agencies coming from without by the food we introduce into our body. 2. _Endogenous obesity_, having its origin within our economy, and depending on changes in certain glands which govern the processes of oxidation—e.g., thyroid sexual glands, pituitary body. This second form is independent of our feeding. As we have shown, this latter can be produced by any of those agencies which are harmful to the ductless glands, especially the thyroid and sexual glands, as, for example, infectious diseases, frequent pregnancies, certain toxic products (alcohol), sexual excesses, climateric. All these conditions may have the effect of producing obesity, which can be explained by an exhaustion of the thyroid and ovaries following a pre-existing hyperactivity. The influence of the ovaries upon the production of obesity can be demonstrated by the sequels of castration, and also by the fact that women, after one or more, especially several pregnancies, or after sexual excesses, may become very fat. In such women this obesity may be only partial and limited (as we have shown in a recent communication to the International Congress of Medicine in Lisbon, 1906) to certain parts—e.g., the mammary glands or hips. There can be no doubt that the sexual glands influence the nutrition of the tissues in a powerful manner, and this has also been shown, experimentally, by the researches of two Berlin experimenters, Professors Loewy and P. I. Richter,[38] performed in the physiological institution of Professor Zunz. These savants have shown that after castration there is a diminution of oxidation. By giving extracts of dogs’ testicles to castrated male dogs, they were able to augment the processes of oxidation. These processes, however, were still more increased after the administration of female extracts to these castrated male dogs. The administration of ovarian extracts to the spayed bitch has, of course, given still better results. Thus there was here an increase of 67.7 per cent. after castration, and 37.6 per cent. of the original value. The increase of the oxidation in male dogs was 44.5 per cent. after castration, by the treatment with ovarian extracts, and 24.8 per cent. above the normal value. If the results after feeding with male extracts were not so successful, it must be attributed to the circumstance that we are at present unable to produce testicular extracts of the same efficacy as ovarian extracts. Footnote 38: