PROBLEMS CONCERNING THE TUMOR VIRUSES 357 



cell-free centrifuged or filtered material from AK/n spontaneous leukemias 

 and with similar materials from induced leukemias, parotid tumors, and 

 sarcomas in C3H mice. Thirty-four induced sarcomas were used to procure 

 transplantable tumors. Cell suspensions were used to transplant 28 of these 

 and only 10 were transplantable. When pieces of the 6 other primary tumors 

 were used as inocula all were transplantable. This latter finding is in accord 

 with almost all other recorded efforts in the literature when sarcomas arising 

 in inbred C3H mice were transplanted into other members of their strain of 

 origin. It would be of interest to know whether extracts prepared from these 

 transplanted sarcomas, or sarcomas induced with a chemical carcinogen in 

 C3H mice, would produce leukemia or parotid tumors in other C3H mice, 

 because when Gross used materials from C3H sarcomas, induced with extracts 

 of leukemic tissue, to inoculate 355 C3H mice, 26 developed leukemia, 19 

 developed parotid tumors, 13 developed subcutaneous sarcomas, and 157 

 mice were alive and tumor-free at a mean age of 11 months. 



Woolley and Small (1956, 1957) confirmed the occurrence of sarcomas in 

 the Bittner substrain of C3H and in Gross' line of the substrain following 

 administration of extracts from AK/n leukemic tissues. They (Woolley and 

 Small, 1956) supported Gross' claim that spontaneous sarcomas were very 

 rare in C3H mice with the statement: "Parotid-gland tumors and sarcomas 

 are virtually unknown in strain C3H." The writer is not aware of any 

 published data on the occurrence of spontaneous sarcomas in the Bittner 

 substrain other than the statement mentioned above, but it has been known 

 for years that they do appear in the NCI substrain, and Dunn et al. (1956) and 

 Heston (1958) have recorded such information. The spontaneous growths 

 developed at a later average age than those appearing in mice treated when 

 newborn with cell-free materials (Law, et al., 1955). The spontaneous 

 occurrence of these sarcomas does not imply they arose in the absence of a 

 virus. As shown in the discussion of mammary tumors in this chapter, high or 

 low incidences of this tumor may be procured in mice carrying or free of the 

 mammary cancer virus. Hence, a high or low incidence of any tumor within 

 an inbred mouse strain is no reason for assuming that the animals harbor or 

 are free of a tumor virus. Strain C3H mice are highly susceptible to the 

 development of sarcomas at the site of inoculation of carcinogenic hydro- 

 carbons and these tumors should be used to ascertain whether the mice 

 carry a sarcoma virus. 



Dulaney et al. (1957) found 10 sarcomas in 152 mice of the NCI substrain of 

 C3H following inoculation with AK/n leukemia extracts and stated that they 

 arose "chiefly in very old animals." Law et al. (1955) obtained 9 subcutaneous 

 sarcomas in hybrids inoculated with extracts of leukemic tissues; 8 arose 

 in (C3H X C3H/Fg)F 1 hybrids, of which 7 also had parotid tumors, and 

 1 arose in a (C3H X AKR)F X hybrid with parotid tumors. Two subcutaneous 



