Abstract
The present experiments attempt to produce lesions confined to the cortico-spinal (pyramidal) tract in cats. Theoretically, this might be done in the pyramids of the medulla, and both pyramids should be cut to remove all cortico-spinal innervation from even one side of the body. This operation, with survival long enough for Marchi studies, has been described only by Starlinger 1 (dogs) and by Schäfer 2 (monkeys). Lesions of one pyramid only, or of the pyramidal decussation have been reported by a few others.
In the present series, 12 bilateral and 4 unilateral lesions were made in the pyramids in cats. Survival was permitted for varying periods to 24 days. Nembutal and sodium amytal were used as anesthetics. The pyramids were cut through an incision in the ventral aspect of the neck. The findings reported begin with the second day and unless otherwise specified refer to the animals with bilateral lesions.
Posture. The assumption of temporary grossly abnormal postures was observed initially in 5 of the 12 bilaterally operated animals and disappeared in these after a few days. Milder manifestations of defective postural control, such as slipping of the feet on a smooth floor, undue twisting of the pivoting leg on a turn, or an over extension of the toes with a backward position of a limb, were present in practically all animals initially. They almost or entirely disappeared.
Of the more constant early postural abnormalities the most common was a tendency to stand with the hind legs abducted and sometimes also inwardly rotated. Less frequently the forefeet appeared unduly flattened on the floor. Many of the animals assumed at times a peculiar half sitting position, resting the whole of the hind feet from toes to ankle on the floor with the rump some distance above it. They often settled into this position with a peculiar slowness and moved slowly from it into other postures.
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