356 Harris M. Benedict 



attack various tissues with different degrees of success. Those cells that 

 cannot successfully withstand the effects of the poison are weakened 

 and destroyed by the independent predatory cells of the body — the 

 phagocytes. Those plants that die soon after producing their seeds, 

 Metchnikoff believes to have been poisoned by poisons formed in the 

 flowers during seed production, which spread from the flowers to all 

 parts of the plant and kill it. 



Here again the theory is based on the conception that but one part is 

 the cause of senility — that in spite of the fact that all the cells have a 

 common origin in the development of the animal or the plant, only those 

 of one organ are the producers of seniUty. As regards both plants and 

 animals, Metchnikoff's theory is obviously of very hmited apphcation, 

 being inapplicable to animals without the large intestine and to flowerless 

 plants. As regards flowering plants, moreover, the enormous span of Hfe. 

 attained by those that produce annually myriads of flowers and seeds is 

 sufficient to eliminate further consideration of the poisoning theory as of 

 primary value. 



As regards animals, furthermore, Metchnikoff's theory is not so much a 

 theory of senility as a denial of seniHty. In so far as he considers the cause 

 of natural death to result from toxins produced by bacteria, he is denying 

 the existence of natural death. In all bacterial diseases their toxins are 

 the most important factors in the production of harm, whether they 

 are localized in the intestine or in the tissues, and when death results from 

 bacterial toxins it is due to disease, not to senility. 



Disease is an interference with the vital activities, produced by unfavor- 

 able conditions — such as attacks of microscopic organisms inherited or 

 acquired, structural defects in one or another organ, or the like. Senihty, 

 on the other hand, produces an inevitable death in spite of the most 

 favorable external conditions and when all organs are sound. It has 

 been shown that in senile degeneration all tissues have undergone a struc- 

 tural and physiological deterioration, and therefore all organs are involved. 



Attempts to single out one particular organ as the sole agency of seniHty 

 are therefore not supported by evidence and are based on a superficial 

 conception of the process. 



Cell specialization 



As the seed or the egg develops into the mature organism, the embryonic 

 cells gradually develop the typical cytoplasmic characteristics that mark 



