_Prophylaxis of Cancer._ From what has preceded in this and other lectures it can readily be understood that the prevention of cancer lies largely along dietary and hygienic lines, including such medical attention as shall secure healthy action of the secreting and excreting organs. If the figures and facts heretofore given are correct, if cancer has surely been observed to increase under certain conditions of life, if it is found to be absent or relatively rare under certain other conditions of living, if cancer has been known to disappear spontaneously in certain individuals, especially when they have changed their mode of living, it must then follow that when the exactly correct habit and state of life are continually assumed the disease will not occur. In other words, when the blood stream nourishing the tissues is ideally correct, the individual cells of the body perform their functions normally, and as each cell is worn out it is removed by a healthy catabolism and renewed by a normal anabolism, and homologous cells then replace those which have ceased to be able to perform their function. On the other hand, when there is perverted metabolism we have various forms of deranged action, to which we give the names of various diseases, one of which is cancer: here in place of homologous cells maintaining the tissues in a normal condition, we have a malignant metamorphosis into heterologous cells, which take on a disorderly or rampant action, and refuse to assimilate themselves to others, so as to form healthy tissue; we have then a mass of low vitality, tending to easily break down or ulcerate, and to extend their malignant action to adjoining tissues, under the continued influence of a contaminated blood current. When once ulceration has occurred, the ordinary parasitic micro-organisms, which are practically omnipresent, find an acceptable nidus, and aid in the destructive work, and also in the systemic poisoning of the tissues.