Here there seems to be a rational method by which we may strive to strengthen the higher elements of the human body, and so prevent them from growing old. The task, at first sight indeed, seems an easy one, only necessitating the injection of a horse (or other animal) with finely minced atoms of human organs, such as brain, heart, liver, kidney, &c., when serums could be drawn off in the course of a few weeks, capable of acting upon those organs. In reality the process would be a very difficult one to carry out, as human organs are rarely obtainable in a condition suitable for injecting into animals. Post mortems can only be legally made twenty-four hours after death, and there are many other obstacles in the way of removing organs from dead bodies. Even if all these difficulties were overcome, another difficulty that would present itself would be the experimenting with various doses of cytotoxic serums of various strength. It is not therefore to be wondered at that the attempt to reinforce the higher elements of the human organism will require much time. If it be necessary to strengthen the higher elements (nervous, hepatic, renal, and cardiac cells), it is plain that they undergo a progressively weakening process. It would be of the highest importance to ascertain the cause of this, for the knowledge would be a guide to future action. The similarity between senile decay and the diseases entailing atrophy in the more important human organs suggests a similitude in cause. Scleroses of the brain, kidneys, and liver frequently originate in intoxication by poisons such as alcohol, lead, mercury, and so forth, or the disease may be induced by some virus, the virus of syphilis being a common cause. The immense importance of venereal disease as a malevolent factor in the phenomena of old age, is especially manifested in arterial sclerosis. According to the careful investigations of a Swedish doctor, Edgren,[300] published in his “Monograph on Arterial Sclerosis,” one case in every five of this disease is caused by syphilis, and he shows that chronic alcoholism is an even more frequent cause (25 per cent.). These two factors when united are responsible for nearly half (45 per cent.) the cases of arterial sclerosis that occur. Syphilitic virus and alcohol act as poisons which bring about first degeneration and brittleness of the arterial walls, and eventually a weakening of the higher elements of the organism. The phagocytes, being cells of an inferior order, are less sensitive to these poisons, which accounts for their victory over the poisoned elements.