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THE AMEBIC AN NATURALIST [Vol. XLIX 



cells under similar defective conditions of blood-supply. 

 Here also degenerative changes entail a cessation of pro- 

 liferation in a similar manner as in ordinary tissue cells. 

 While farther away from the blood-vessels the tumor cells 

 degenerate and die, near the blood-vessels they continue 

 to live and to multiply. 



While from a theoretical point of view, therefore, the 

 question as to the potential immortality of somatic cells 

 has through the experiments on tumor cells been answered 

 in a decisive manner, it was nevertheless of interest to 

 extend these investigations to ordinary tissues. Such 

 investigations we undertook in the course of the last 

 eight years, and while certain obstacles were encountered, 

 which prevented the continued life of ordinary tissues, the 

 results were of interest in giving an insight into some of 

 the conditions which determine the growth, life and death 

 of somatic cells. These investigations have shown that if 

 tissues are transplanted into another individual of the 

 same species, under the influence of the constitution of 

 the body fluids, which differs in different individuals of 

 the same species, the metabolism in the transplanted 

 tissues is interfered with as shown, for instance, in patho- 

 logical differences in pigmentation seen in black skin of 

 the guinea-pig after transplantation into other animals of 

 the same species. After transplantation of pigmented 

 skin into the same individual in which it originated, such 

 pathological changes do not occur. As I have previously 

 pointed out, a certain adaptation exists between the 

 tissues and body fluids in animals of the same species, and 

 even between the tissues and body fluids of the same indi- 

 vidual. Thus it comes about that the interaction of tis- 

 sues and body fluids of the same species leads to different 

 and less toxic products than those produced through the 

 interaction of the body fluids of one with the tissues of 

 another species. Even the interaction of tissues of one 

 animal with the body fluids of another animal of the same 

 species leads to more toxic products than the interaction 

 of body fluids and tissues of the same individual. In the 

 latter case toxic products, interfering with the life of 



