Animal Behavior and Internal Drives

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Abstract
The movement of caged animals was studied through the use of apparatus which carefully recorded all motor activities. External stimulation was eliminated so that whatever movement occurred could be attributed to inner drives. The white rat showed rhythmic periods of motor activity about every 2 hrs. Food was sought about as often. The empty and strongly contracted stomach coincided with maximum motor activity in the rat. Attempts to correlate this action with the gastric contraction failed. In the human adult the greatest gastric contractions were accompanied by the greatest amount of body activity during sleep. Richter concluded that the hunger contractions stimulate the animal to activity and are responsible for the rhythmicity of his motor drives. In the new-born rat more or less continuous restlessness is noted until food is located. Later the motor activity tends to become rhythmic. The [female] rat showed a greatly increased activity every 4 days. This was most marked just before ovulation. It disappeared if the ovaries were removed or if the animal became pregnant. It reappeared if the ovaries were successfully transplanted. It was absent in [male] rats and tended to appear if ovaries were transplanted in [male] rats after the testes were removed. This increased rhythmic activity every 4 days the author concludes is directly or indirectly dependent on an ovarian hormone. Defecation and urination are also periodic in the rat. A close relationship was established between nest building and body heat. Burrowing and huddling also represent attempts at heat conservation through motor activities. The author has established the relationship between automatic physiological body processes and general motor response.

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