CLINICAL AND ANATOMICAL STUDIES ON TWO CATS WITHOUT NEOCORTEX

Two cats without neocortex are described clinically and anatomically. In the first both cerebral hemispheres were removed anterior to the thalamus; this animal lived for nine days after the second operation. It exhibited states of waking and sleep, and when awake it made purposeless circus movements. It did not eat spontaneously. In the other animal the rhinencephalon and striatum were left intact; this animal was kept alive for five months after the second operation. Immediately after the second operation it showed much more activity and a greater variety of movements and of reactivity than the thalamus cat. It reached and ate its food spontaneously, and for a time it had polydypsia, polyphagia and polyuria, which were probably due to destruction of the right nucleus filiformis. Immediately after the operation the animal developed a well-marked shaking reflex of the extremities; this was shown to be an exaggeration of the normal shaking reflex which serves to clean or dry the paws. The animal cleaned its fur spontaneously. Its motor activity, when recorded in an “activity cage,” was found to be much greater than that of a normal cat. This excessive activity was excited by noise, and increased during infection by nematodes and mange. Rotational nystagmus and after-nystagmus were studied on a rotating wheel, and were shown to follow the same rules as in intact animals and in man. As long as the speed and the amount of rotation were kept within physiological limits, the number of jerks depended chiefly on the degree of rotation. On longer rotation the after-nystagmus assumed the characters of a reaction to acceleration. Electrical stimulation, immediately before the animal was killed, of those portions of the brain which remained revealed two points which were definitely excitable. The first proved to be the anterior commissure; stimulation of this produced movements relating to smelling and eating, as puckering of the nose, licking, moving the whiskers and chewing. The second point lay above a small comma-shaped nucleus in the velum medullare; stimulation of it gave rise to urination and changes in the respiratory rhythm. The anatomical examination showed that, on the whole, the aim of the operations had been attained; the few portions of the neocortex which had been left had no fibre connections with the brain-stem. The anterior and lateral parts of the thalami had undergone severe atrophy. This atrophy was more marked on the left side on which the striatum had been damaged.