HYPER TROPHY I 1 7 



brought to the kidney in the blood ; fifth, this food is taken up in 

 larger amount than before by the cells, which leads to an increase in 

 the growth of the cells, which produces hypertrophy. The increase 

 in size, looked at from this point of view, Nothnagel says, has nothing 

 mysterious about it. The enlargement seems to be an adaptation ; but 

 the enlargement does not take place because it is an adaptive process, 

 but because it cannot be helped under the conditions that arise. We 

 shall return again to Nothnagel's interpretation, when we come to 

 consider other views. 



' Experiments of the sort just described are most easily carried out 

 on the paired organs of the body, such as the salivary glands, the 

 tear glands, the mammae of the female, and the testes of the male. 

 In regard to the latter two organs the evidence, especially in the case 

 of the testes, is conflicting, but the recent experiments of Ribbert 

 seem to give definite results. Nothnagel had found that after the re- 

 moval of one testis there is no hypertrophy of the other. He pointed 

 out that this result does not stand in contradiction to his hypothesis 

 in regard to the kidneys, for the loss of one testis does not lead to 

 a greater functional activity in the other. Each acts for itself alone. 

 The result shows further, he adds, that the process of hypertrophy 

 is not an adaptive one, but a physical or a physiological process. 

 Ribbert on the contrary thinks that even Nothnagel's statistics give 

 evidence of hypertrophy, and Ribbert's own experiments give un- 

 mistakable evidence of a considerable enlargement of the remaining 

 testis. In his experiments, young rabbits were used that were born 

 of the same mother and in the same litter. One of the testes was 

 removed from some of the individuals, and after some months the 

 remaining testis was taken out and its weight compared with that 

 of the control animal. In sixteen out of seventeen experiments there 

 was found to be a noticeable increase in the single testis as compared 

 with either testis of the control animal. The results show that in 

 some cases the single testis weighs almost as much as the two to- 

 gether of the control animal. It is important also to notice that 

 in this case the enlargement has taken place in an organ that has not 

 been active, as was the case with the kidney. 



Ribbert has also shown that hypertrophy takes place in the 

 mammae of the rabbit after the removal of some of them. Five out of 

 the eight mammas were removed in three cases, and seven out of the 

 eight in two other cases from young rabbits about two months old. 

 Ribbert found that if the operator is not careful to remove completely 

 all the tissue of a mamma an active regenerative process takes place 

 from the part that remains. After five and a half months the single 

 remaining mamma of one animal measured six and one-half by three 

 and four-fifths centimetres, and the corresponding one in the control 



