ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. V.

Young rats bearing a mass of 1.06 gm. both at shoulder level on the back and posteriorly at the sacrum exhibit in their geotropic progression a relationship between angle theta of oriented path and inclination alpha of substratum which differs from those obtained with rats of the same race carrying the same total added load concentrated anteriorly or posteriorly. The distributed load affects more or less equally all the groups of receptor units concerned in tension excitation. It is shown that the variation of orientation is organically determined, quantitatively, by the intensity of tension excitation, regardless of the imposition of the added loads. The bearing of these facts upon the theory of the geotropic orientation is discussed.