Tumor-inducing properties of the mammary tumor agent in young and adult mice.
The mammary tumor-inducing activity of the mammary tumor agent was studied by the administration of either one or five injections of fractions of transplanted mammary cancer into mice ranging in age from 22 to 126 days.

The concentration of the fractions represented the amount of the agent derived from either 2 × 10-2 or 10-3 gm. equivalents of fresh tissue.

In general, the incidences observed in adult mice could not be correlated with the amount of the agent that was injected.

The highest incidence occurred in the progeny of the mice which received a single injection of the fraction with the lowest concentration of the agent.

The transmission of the agent was observed following the administration of the mammary tumor agent into both young and adult females.

No significant difference was to be seen in the transmission of the agent in the milk of either cancerous or noncancerous experimental mice.

Data were presented suggesting that the age resistance to the tumor-inducing action of the mammary tumor agent may be determined, in part, by the genetic constitution of the test animals. Other possibilities were discussed.
Assay of frozen mouse mammary carcinoma for the mammary tumor milk agent.
Summary Salvin-Moore, in 1908, determined that tumors would develop in mice following the subcutaneous implantation of neoplasms which had been exposed to the temperature of liquid air (−195° C.). He proposed a virus theory to explain the results, although he considered the possibility that some cells had remained viable. In 1949, Gye and his associates submitted a similar theory based upon observations obtained following the freezing and drying of mouse cancers. Furthermore, Mann stated that when mammary cancers (both transplanted and spontaneous) were frozen, the milk agent virus was liberated in its “active” form and when injected subcutaneously, mammary tumors would be produced at the site of injection within a short interval of days or weeks. Few mammary tumors arose at other sites of inoculation because of the “selective infectivity” of the virus for mammary tissue. To test for the active mammary tumor milk agent virus, transplanted mammary tumors were minced, suspended in dextrose, and frozen to −79° C. The thawed tumor-mince produced mammary tumors at the site of injection only in mice of stocks which would be susceptible to fresh tissue grafts of the tumor being tested. Negative results were obtained with mice of other strains, although they were susceptible to the development of spontaneous mammary cancer. Intraperitoneal inoculation of the frozen material was as effective as subcutaneous injection in the production of mammary tumors. Whereas cell-free centrifugates have been found to contain the mammary tumor milk agent, cell-free extracts of the frozen mammary tumor-mince failed to induce tumors, within the specified interval, in any animal regardless of its genetic constitution. Preliminary data indicate that the milk agent was no more active in cell-free extracts of the frozen than the fresh tissue of the same tumor, regardless of the route of administration. The final results of these tests will not be apparent for months, but the earliest tumors to be observed developed in mice which had received intraperitoneal injections. The revival of this viral theory for mouse cancer by Gye et al. and Mann disregarded the previous finding of many investigators that mouse tissues (normal and cancerous) survived freezing to low temperatures. Evidence was also cited that the newly designed desiccator, used for their studies, did not destroy all cells. The fact that other methods of dehydration, including their own studies, had given negative results which would refute the virus hypothesis was disregarded as due to imperfect technic. The experimental data submitted by Gye et al. and Mann were, without a doubt, based upon observations which they either incorrectly interpreted, as in the case of the studies with frozen tissues, or secured by using new equipment before it had been adequately tested and which resulted in imperfect technic.
Archaeology and mud wall decay in a West African village
Abstract A detailed study of the processes of deterioration of mud walls and of the physical evolution and devolution of a contemporary West African village is seen to facilitate the location of decayed mud structures at a nearby archaeological site. Various climatic and pedological conditions at the site make it unlikely that such walls will be discerned. The archaeologist wishing to obtain the fullest and least biased picture of the settlement configuration of the ancient community should therefore heed all the inferential lessons to be had from a focused ethnographic investigation. Given similar climatic situations and practices of house construction, taphonomy and ethnographic analogies may both be necessary for a valid reconstruction of an archaeological settlement.