1911.] The Viability of Human Carcinoma in Animals. 193 



of events occurring after implantation was as follows : — In naked eye aspect 

 the tumour, which was usually easily recognisable, being moist and greyish in 

 aspect and lying loosely among the tissues of the host, did not appear much 

 changed during the first two days. After this period it became dry and 

 increasingly adherent to the surrounding tissues, from which it was less 

 readily distinguished after the fifth day. On microscopic examination the 

 central portions of the growth were found to have undergone necrosis during 

 the first two to three days, presumably in part, at any rate, owing to 

 defective supply of oxygen. Some of the cells at the periphery of the 

 implanted mass, on the other hand, at first remained unchanged in appearance 

 and exhibited more or less evidence of proliferation, generally presenting for 

 the first two to four days mitoses, though fewer in number than was 

 exhibited by the growth before implantation. After the fifth day all the cells 

 of the implanted tumour had become altered and ceased to exhibit mitoses ; 

 their nuclear chromatin no longer presented the usual arrangement, but had 

 become collected into irregular masses or fragments. Accompanying the 

 necrotic changes occurring in the portions of tissue implanted, leucocytes, 

 mostly polynuclear, made their appearance in large numbers, being replaced 

 subsequently by mononuclear cells before which the remains of the implanted 

 tissue disappeared. The disappearance of a piece of tumour of the form of a 

 millimetre cube appeared to be completed after the second week of 

 implantation. 



In the summary given in the table the proportion of observations in which 

 living cells and mitoses were noted during the first five days after 

 implantation is given in a percentage form. It will be seen that inhibition 

 of the function of cell division is early marked, while cell death occurs (at the 

 periphery of the implanted mass) more slowly. If the experiments made 

 upon the monkey alone are considered, the percentages obtained are more 

 regular, being respectively : 67 and 25 on the first day ; 69 and 8 on the 

 second day ; 67 and on the third day ; 37 and 12 on the fourth day ; 20 and 

 20 on the fifth day. The experiments made with animals other than the 

 monkey are too few in number to yield percentage values, but the 

 circumstances that mitoses were not met with after implantation suggests 

 that human carcinoma is less viable in these animals than in the monkey. 



The result of implanting human carcinorha upon animals, it will be observed, 

 is similar to that of implanting mouse carcinoma upon rats already referred 

 to. In both cases a limited degree of inoculability is observable, some of the 

 implanted cells continuing for a time to live and to divide, but whereas in the 

 latter case the rate of proliferation is at first little affected and regression 

 does not begin till the eighth to the tenth day, in the present experiments the 



