Identifier: effectsofinbreed1090wrig (find matches)
Title: The effects of inbreeding and crossbreeding on guinea pigs : I. decline in vigor : II. differentiation among inbred families
Year: 1922 (1920s)
Authors: Wright, Sewall, 1889-1988
Subjects: Guinea pigs
Publisher: Washington, D.C. : U.S. Dept. of Agriculture
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Fig. I.— Male of Family 39, Belonging to the Thirteenth Generation of Inbreeding. £&. 1 . • - :^/~- ifalfratu^ ^!!3*,^^^^^^i^»^^ r, w Fig. 2.—Female of Family 39, Full Sister of the Male Shown Above.The Small Amount of White and the Sway Back Are Character-istics Fixed in this Family. Other characteristics are the greatest success in bearing young alive, but lack of successin rearing them, irregularity in producing litters, and the greatest susceptibility totuberculosis. Bui. 1090, U. S. Dept. of Agriculture. PLATE VI,
Text Appearing After Image:
Four Generations of Family 35. The young pair at the right is descended from 19 generations of matings of brother with sister.Their parents, grandparents, and great-grandparents were all found to be alive and are shownin the picture. There is little if any genetic variation left in this stock. The variation in pat-tern, which persists, seems to be due to nontransmissible irregularities in development. EFFECTS OF INBREEDING AND CROSSBREEDING. 17 shown above. Most of the variation within litters thus must bedue to such a cause as position in the uterus. Seasonal conditions have a marked effect on birth weight throughtheir influence on the condition of the dam. The age of the dam isnot an important factor. The gain in weight between birth and133 days is affected by thesame factors which affect the prenatal rate of growth, namely, sizeof litter, condition of dam, and heredity. The correlation between gain and size of litter in the same data asthose used above was —0.381 ±0.011. That be

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