Neurasthenia is a disease which, as we have tried to show, is very often based upon changes in the ductless glands, especially the thyroid, sexual glands, and pituitary body. The same holds good for hysteria. Therefore the presence of such conditions will influence us in our judgment as to the future of such persons. In cases of great nervousness, especially when associated with mental depression, there is less resistance to infection, for causes already mentioned (see Chapters III and L). Great mental excitability may predispose to certain diseases which shorten life, like diabetes, and in people in whom, owing to an unstable nervous system, there is a frequent increase in the blood-pressure, the possibility of apoplexy is to be feared, if such persons are of a plethoric build. The wear and tear of life is certainly far more felt by persons whose minds are very easily impressed and excited by events of little importance; and, considering the great influence of mind upon body, persons, who like a weak tree are easily beaten down by the smallest storm, will have less chance of long life than persons who have a better control over themselves and stronger will-power (see “Hygienics of the Mind,” Chapter L). Having thus briefly described the principal functions governed by the thyroid gland: shown how, by observing changes in these functions, we can judge as to the healthy condition of this gland, let us now see if any means exists by which we can ascertain the functionating condition of the other ductless glands. After the thyroid the sexual glands claim our attention, as these glands are of the utmost importance on account of their enormous influence upon the processes of metabolism and the maintenance of life (see Chapter V). We must first call to mind that their work is essentially under the influence of the thyroid, changes in which invariably produce changes in the sexual glands. Thus, in degenerated conditions of the thyroid, we find impotency in men and sterility in women. In such conditions atrophy of the testicles, or of the ovaries, can often be found. These clinical observations can be confirmed by experiments. Thus Lanz[122] found sterility common in goats whose thyroids had been extirpated. In cretins an atrophic condition of the testicles, or of the ovaries, is present as a rule, and such patients very frequently show lack of sexual desires. Footnote 122: Lanz: Loc. cit. Direct examination of the sexual glands can be more easily carried out in men than in women. The presence of varicose veins is of great importance, as varicoceles are generally accompanied by great disturbances of the nervous system, sometimes even going as far as insanity. Suicide is not unfrequently committed in such a condition.