Carbonic Anhydrase in the Pallium of Primates Compared with that of Lower Mammals.

Abstract

In the dog, hog and cat a greater content of the enzyme had been found in the cortex than in the white matter lying immediately beneath it. In man, the reverse relationship of a greater content beneath the cortex had been observed except in the motor area, where the relationship was that of the lower animals. Extension of the study to the rhesus monkey, the horse, rabbit, and sheep has shown in the monkey a pattern like that of man, and in the horse, rabbit, and sheep the pattern of distribution reported for the dog, hog, and cat. The data indicated that the reversed relationship between the. enzyme content of the cortex and the underlying white matter in man was due to an increase beneath the cortex rather than a decrease in the cortex. The difference was less in the occipital pole, where there was a preponderance of point to point projections from the geniculate nucleus and fewer extrinsic cortico-cortical connections, than in other areas where the extrinsic cortico-cortical connections occupy a greater proportion of the white matter. It was concluded that the pattern of distribution of this enzyme, found in man and the rhesus monkey, might be part of an evolutionary development distinguishing the primate brain from that of the lower mammals.