deleterious influence upon almost all the tissues of the body, the functioning of which it is more easy to estimate. For example, the cells of the skin and of the mucous membranes which happen to be visible to the eye show clear evidence of diminished vitality and increased vulnerability. Physiological stimuli, incapable of producing any visible reaction in healthy children, habitually determine widely spread and persistent inflammatory reactions. For example, the licking movements of the tongue at the corners of the mouth produce the little unhealthy fissures which the French call _perlèche_. The physiological stimulus of the erupting tooth is capable of causing a painful irritation of the gum, so that the child is said to suffer from teething, accompanied, it may be, and the association is significant, by "teething convulsions." The irritation of the urine produces rawness and excoriation of the skin of the prepuce, contact with intestinal contents not in themselves very abnormal, an intractable dermatitis of the buttocks or a persistent diarrhoea and enteral catarrh. Improvement in the general health, the result of the cessation for the time being of the recurrent infections, perhaps consequent upon improved hygienic conditions, always determines the rapid disappearance of all these accompaniments of the general diminution of tissue vitality. The muscular system and the bones are commonly also involved, so that rickety changes are often found in these infantile and watery children. In early childhood the processes of calcification and decalcification proceed side by side and with great rapidity, and in health there is always a balance on the side of the constructive process. In the children whom we are now considering, saturated as they are, from time to time, with the toxins resulting from repeated infection, ossification may be so interfered with as to cause softening and bending, with the evolution of a state of rickets. Between bone and muscle, too, we find a close relationship. We do not find powerful muscles with softened bone, nor flabby muscle with rigid and well-formed bone.