The Effect of Added Loads upon the Geotropic Orientation of Young Guinea Pigs

It has been found that young guinea pigs when progressing over a surface inclined at an angle alpha with the horizontal, orient upward in a way such that the path described by an oriented animal is at a mean angle theta with the base of the inclined surface. The magnitude of mean theta increases as the angle of inclination alpha increases. The function relating theta and alpha is compound, being made up of two sections with a break which corresponds to a change in the mode of progression of an animal over the surface of the plane. If a load of constant relative mass is attached to the back of an animal, midway between the fore and hind legs, testing on an inclined surface reveals the fact that the magnitude of mean theta is increased over the entire range of stimulation, with the two values of mean theta (i.e. with and without added load) becoming more nearly equal as they approach 90 degrees as a limiting value. The variation (P.E. of mean theta) is not sensibly changed by attaching a load to an orienting animal; for equal magnitudes of theta, under the two sets of test conditions, the P.E.'s are very nearly equal.