Geotropic Orientation of Young Mice

The upward geotropic orientation of young rats can be described by simple mathematical expressions (Crozier and Pincus, 1926, 192627, a, b; Pincus, 1926-27). In essence these formulae also apply precisely for the geotropism of invertebrates (Wolf, 1926-27; Crozier and Stier, 1927-28; Wolf and Crozier, 1927-28). I t seemed important to repeat with young mice the initial experiments with rats (Crozier and Pincus, 1926-27, a), partly as an independent test of the general results and in further part to investigate objectively certain sources of variation inherent in data obtained as averages from observations upon numerous individuals. Young mice proved to be not such good material for these experiments as the rats. Their creeping is more irregular, interrupted. The stock used was not of a genetic homogeneity comparable to that of the rats (lot. cil.), having been inbred for but four generations. The extent of average upward orientation on an inclined plane is nevertheless found to be a definite function of the active gravitational component, and the results are, in fact, closely comparable to those earlier secured.