No. 641] INHERIT AXCE OF CANCER IN MICE 511 



ing the effect of In^bridization on the cancer rate. This 

 was made possible to us in 1910 through the interest 

 which Miss Lathrop, who bred a very extensive stock of 

 mice, took in these plans and with her cooperation we 

 carried out these breeding experiments from 1910 on 

 through a considerable number of years. In the following 

 year we published the record of a cancer family of mice 

 which we had observed through several generations (4). 

 Altogether we carried out observations on approximately 

 12,000 female mice reaching the cancer ago which we fol- 

 lowed throughout the whole period of their life and which 

 were observed through successive gonerntions. 'Mimy of 

 them were used for hybridization. 



In the meantime E. E. Tyzzer had published in 1907 

 and subsequently studies of the inheritance of cancer in 

 mice (5). This author found indications that heredity 

 may play a part in the etiology of animal cancer. Some- 

 what later Murray undertook similar slndics in wliicli ho 

 used methods similar to those previously cniijh.yrd in 

 the study of human cancer. This author compaiTd the 

 frequency of caiiccr nnioiig individuals wliosi' mother or 

 grandmothci- had cancel- on the one hand, and among 

 those in whom cancel- had not Iteen ohscrved in the direct 

 ancestry but may have occurred in the groat grand- 

 parents (6). Murray found on the average about 20 per 

 cent, of cancerous mice among those whose direct an- 

 cestors had suffered from cancer and 11 per cent, among 

 those whoso direct ancestry had l)eon free from cancer. 

 In certain a-v c]a->e- the cancer rate of both kinds of 

 mice showed onl\- a \ er> slight di fforenco and in (mo age 

 class the cancer rate was even hi.u'hor in tho-e whose 



These result> as well a> mh,- prcvimis'stn.lie. and ^onio 

 occasional oh.servations of Alhrecht and llecht an<l of 

 Spronk and a few others made wvy prohalih' the -iunifi- 



of Ijorrel antl others who referred tiio ondeniic occurrence 



