A Long-Term Study of the Experimental Neurosis in the Sheep and Dog with Nine Case Histories: By O. D. Anderson and Richard Parmenter. Psychosomatic Med. Monograph Vol. II, Nos. III and IV. Washington: National Research Council, 1941. 150 pp.

Out of a total of twenty-eight sheep and twenty-six dogs studied, the authors succeeded in inducing an experimental 'neurosis' in seven sheep and three dogs. The dogs with experimental neurosis

were observed over a period of four years and the sheep for twelve years.

The first step in the experiment was the setting up of a conditioned reflex effected by utilizing a new method: a stimulus, such as a sound, was reënforced by the application of a mild electric shock to the forelimb of the animal; the motor response to the stimulus or the shock was a defensive flexion movement of the limb accompanied by movements of the head and trunk. To precipitate an experimental neurosis several measures were now introduced. One consisted of making the differentiation of stimuli difficult. It was found, for example, that the sheep formed a positive conditioned motor response to a metronome beating at the rate of 120 per minute, reënforced by a mild electric shock, and was able to distinguish between this metronome and one beating at the rate of 50 per minute and not reënforced by a shock. When the negative stimulus was then gradually advanced until the metronome rate was 100 per minute, discrimination broke down and experimental neurosis set in, while all conditioned responses disappeared. The same results were obtained when the procedure was varied so that, instead of the positive and negative stimuli alternating, a positive stimulus was succeeded by a long series of negative stimuli. A third method for producing the experimental neurosis consisted of setting up a rigid time schedule; instead of alternating a positive and negative stimulus at variable intervals of time, the interval was made a fixed one. The time required to induce the neurosis was thought to depend upon the genetic susceptibility of the animal, the intensity of the testing schedule, the strength and probably the unpleasantness of the unconditioned stimulus. It varied from ten days in one sheep to seven