The occupations employing mercury, whether mining, mirror-making, or gilding, produce forms of systemic nervous exhaustion in which the most marked symptom (but less important from a sanitary standpoint) is a tremor amounting at times almost to shaking-palsy. Like all other systemic nervous exhaustions, the mercurial one may appear as degeneracy in the offspring. The employment of women in match factories and tenement house sweating shops is growing. The chief toxic effect of phosphorus is not the localised jaw necrosis. This is but an evidence of the progressive system saturation with phosphorus. It bears the same relation to the more dangerous effects of phosphorus that "blue gum" does to the systemic effects of lead. Every condition arising from a toxic cause capable of producing profound systemic nervous exhaustion in the ancestor, and especially the ancestress, is likely to be transmitted as degeneracy to the descendant. Undoubtedly with the growing tendency of woman to pass from the ill-paid work of the seamstress to the better paid but dangerous occupations, a certain seeming increase in degeneracy must result. CHAPTER VII CONTAGIOUS AND INFECTIOUS DISEASE Among the gains of human advance in evolution stand out prominently complete immunity from certain diseases due to germs, and partial immunity from others, which last immunity results in chronic types, rather than in acute, because of increased vital resistance in man. Tuberculosis and dourine, acute diseases in the cow and horse, have become chronic diseases, tuberculosis (or consumption) and syphilis, in man. Such chronicity is evidence of advance, yet it constitutes an element of degeneracy, since the victim of the chronic disease is able to leave more offspring than would be possible were the disorder acute. In other respects acute and chronic contagions and infections exert the same influence in regard to degeneracy. The germ of the disease may be inherited, or general nutrition of the foetus may be so checked in development that the child inherits a predisposition to disease. Through this check to foetal development the phagocytes, or white blood cells, become so weakened that they are unable to devour foetal structures as useless to man as the tadpole's tail (which it devours) is useless to the developed frog. This power being weakened, the organs which form antitoxins (or protective tonics against disease), from lack of development fail to perform their function. For this reason in the degenerate many infections and contagions assume their old destructive type.