Later on, I myself[296] tried to complete the work, and for the purpose made use of the published results of all the investigators who had studied senile degeneration. I gave a summary of my conclusions in the following words: “In senile atrophy the same condition is always present: _the atrophy of the higher and specific cells of a tissue and their replacement by hypertrophied connective tissue_.” In the brain, the nerve cells disappear; that is to say, the cells which subserve the higher functions such as intellectuality, sensation, control of movement, and these are replaced by elements of a lower kind, in especial by neuroglœa, a kind of connective tissue of the brain. In the liver, the hepatic cells, of great importance to the nutrition of the organism, yield to connective tissue. In the kidneys, that tissue invades and blocks the tubes by which the necessary process of eliminating soluble waste matter is accomplished. In the ovaries, the ova, the specific elements which serve to propagate the race, are similarly eliminated and replaced by granular cells, a variety of connective tissue. In other words, a conflict takes place in old age between the higher elements and the simpler or primitive elements of the organism, and the conflict ends in the victory of the latter. This victory is signalised by a weakening of the intellect, by digestive troubles, and by lack of sufficient oxygen in the blood. The word conflict is not used metaphorically in this case. It is a veritable battle that rages in the innermost recesses of our beings. Distributed throughout every part of our bodies are certain cells which fulfil special functions of their own. They are capable of independent movement, and also of devouring all sorts of solid matter, a capacity which has gained them their name of phagocytes or voracious cells. The function these phagocytes fulfil is a very important one, for it is they that congregate in vast numbers around microbes or other harmful intruders, in order to devour them. Effusions of blood and other elements, on penetrating to parts of the body where their presence is disadvantageous, are absorbed by these phagocytes. In cases of apoplexy, where blood is shed into a part of the brain, setting up paralysis, the phagocytes cluster round the clot and devour the blood corpuscles it has encased. This absorption is a lengthy process, but by degrees, as the pressure of the effusion of blood is removed from the brain, and paralysis disappears, the health of the organism may become completely restored, recovery in such a case being due to the work of the phagocytes. After childbirth, when the uterus presents the appearance of a great open wound clotted with blood, it is again the phagocytes that clean it and re-establish the normal condition. It is plain, therefore, that the part played by these cells is beneficent.