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.
RECENT STUDIES ON THE MOUSE MAMMARY TUMOR AGENT
it was demonstrated that the MTA could be administered in extracts of either normal or cancerous tissues from infected mice1216-20 including seminal vesicles2' and cauda epididymidis.22 During the past ten years various workers have found that, in certain matings, when agent-free females of some inbred strains, either susceptible or relatively resistant to the development of spontaneous mammary cancer, were mated with males of cancerous strains, a relatively high incidence of mammary cancer might be observed in the progeny, especially in those born in the later litters. It has been accepted that the development of these tumors was dependent upon the transfer of the agent by the male, first infecting the mother, who then transferred the MTA to her offspring in her
An introduction to human geography : the cultural landscape
1. Thinking Geographically 2. Population 3. Migration 4. Folk and Popular Culture 5. Language 6. Religion 7. Ethnicity 8. Political Geography 9. Development 10. Agriculture 11. Industry 12. Services 13. Urban Patterns 14. Resource Issues Conclusion