Proceedings of the First National Cancer Conference / American Cancer Society and the National Cancer Institute of the U.S. Public Health Serivce, Federal Security Agency.
- National Cancer Conference 1949)
- Date:
- 1949
Licence: Public Domain Mark
Credit: Proceedings of the First National Cancer Conference / American Cancer Society and the National Cancer Institute of the U.S. Public Health Serivce, Federal Security Agency. Source: Wellcome Collection.
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![uniformity has been reached. An inbred line declines toward the level of certain homozygous combinations, different in each char- acter in each line. Figures are somewhat misleading in reference to vigor. Great differentiation among inbred lines in relatively neutral respects, depending on which combination of genes of the founda- tion stock happens to be fixed, is obviously another expectation. This differentiation may indeed be expected to go far beyond that visible in the foundation stock. Finally under the mendelian interpretation, the crossing of random inbred lines may be expected to lead to full restoration of the vigor of the foundation stock. If there has been selective elimination of lines in which the more unfavorable genes have been fixed, crossing may lead to a stock superior to the original. It may, however, require two generations to get the full effect, because of the physiological influence of the inbred mother on the first generation crossbreds. EFFECTS ON MORTALITY AND FECUNDITY The results of the guinea-pig experiments were in good agree- ment with these expectations. Let us illustrate this by consideritg mortality at birth during the period 1916 to 1919. Figures 1 to 7 compare the averages for the control stock B, the five larger inbred strains, and the average of the others, first crosses (CO) progeny of crossbred male with unrelated inbred female (CA), the recip- rocal (AC) progeny from two unrelated crossbreds (CC), and the results from renewed inbreeding (Cl, C2). Certain corrections have been made to obtain maximum comparability. The lowered viability of even the best inbreds after nine years of inbreeding, the considerable differentiation among the strains, the dependence of crossbreds on the breeding of the mother (a poor record where the mother was inbred [CO, CA] but a good one where crossbred [AC, CC, Cl], and decrease on renewed inbreeding of the mother (C2) are all brought out. Figures 1 and 2 show averages for the percentage reared of those born alive. The results differ from the preceding in the immediate improvement on cross breeding. Young guinea pigs are](https://iiif.wellcomecollection.org/image/b3217133x_0029.jp2/full/800%2C/0/default.jpg)
