356 H. B. ANDERVONT 



mice with tumors were limited to 6 of 17 litters. These were the first tumors 

 of this type to be produced in AKR mice and Dulaney's results, together with 

 those of Woolley and Small (1957) suggest that the induction of parotid 

 tumors in an inbred mouse strain may depend upon the kind of treatment to 

 which the animals are exposed. 



Dulaney et al. (1957) recorded the occurrence of parotid tumors in C3H 

 mice of different substrains after they had received cell-free leukemia extracts. 

 These tumors arose in 7 of 152 mice of the NCI substrain and in 5 of 45 

 animals of the Bittner substrain. No direct statement was made concerning 

 the limitations of parotid tumors to certain litters but the occurrence of 

 5 parotid tumors in a litter of 5 mice was mentioned. Extracts of leukemias 

 from AK/n mice inoculated by Gross or from AK/n mice bearing transplants 

 of this tumor were more effective in producing leukemia, parotid tumors, and 

 sarcomas than those prepared from spontaneous or transplanted leukemias 

 in AK/n or AKR mice raised in their own laboratory. They also included a 

 statement that cell-free extracts from parotid tumors were used to carry the 

 virus through two serial transplant generations. Continuation of this animal 

 passage strain should yield a virus which will be available to other investi- 

 gators. 



3. Sarcomas 



Gross (1955a) first mentioned the occurrence of sarcomas in his experi- 

 mental animals in a footnote by stating: "Among mice which developed 

 parotid gland tumors, several also developed subcutaneous fibrosarcomas." 

 In a later paper (Gross, 1955c) more specific data were presented. Centrifuged 

 or filtered extracts from induced leukemias, or induced parotid tumors in 

 C3H mice, and centrifuged extracts from normal lactating mammary glands 

 of C3H mice, were injected into C3H animals, of which some developed 

 parotid tumors and sarcomas while others developed sarcomas only. Most of 

 these sarcomas arose in subcutaneous tissues, but some were found in the 

 muscles, in the muscular or perineural fascia, and in the uterus. Gross had 

 never observed sarcomas in untreated C3H mice and, strangely, "only a few 

 of these sarcomas could be transplanted, by cell transfer, in C3H mice of the 

 same substrain." The tumors resembled fibrosarcomas, myxosarcomas, and 

 rhabdomyosarcomas. 



Gross (1956) prepared centrifuged extracts from induced parotid tumors in 

 2 C3H mice and used the material to inoculate 19 C3H mice; 5 developed 

 spindle cell sarcomas at 12-19 months of age. Sarcomas arose in other C3H 

 mice treated with lyophilized and glycerinated AK/n leukemic tissues. 

 Gross again emphasized the fact that he never saw a spontaneous sarcoma in 

 his C3H mice. In his summarizing publication, Gross (1957b) showed that 

 sarcomas were induced in C3H mice after they had been inoculated with 



