Cortex weight: a genetic analysis in the mouse.

Differences in forebrain weight, forebrain weight/body weight ratios, and body weight were examined for the RI strains, their progenitor strains, and reciprocal F1 hybrids. The experiment was done in two widely separated laboratories with identical procedures for feeding, watering, and removal of brain tissue. The resulting strain distribution patterns suggested the influence of two or more loci in each laboratory. However, brain weights differed in the two laboratories. Some of the strains examined exhibited increased weights for the variables under consideration, while others exhibited decreased weights or no change at all. Implications for generalizations drawn from observations obtained in any single laboratory were discussed.