Abstract
Summary
Mice of the ICR/Ha strain were sex-segregated at 21 days of age and were followed for development of neoplasia for a period of 650 days in comparison with groups which were not sex-segregated. There was a high incidence of spontaneous neoplasia in the non-segregated mice and this was principally mammary carcinoma. Incidence of mammary carcinoma was drastically reduced by sex segregation but incidence of other malignancies of minor occurrence was not affected. Injection of extracts of human malignant materials apparently did not influence occurrence of malignancy either in non-segregated or in sex-segregated mice. These findings are discussed in relation to those of Grace et al who reported a high incidence of mammary carcinoma in ICR/Ha mice given human malignant tissue but not in control groups.
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