Morphological and chemical studies of developing cerebral cortex in the cat

101 animals were used for the study of morphological and chemical changes in the suprasylvian gyrus of the cat. The prenatal studies were carried out in the fetuses for 4.5 cm to 12.5 cm. C-R length. The postnatal changes were studies in the cats from 1 day of age kittens to the adult stage. The quantitative morphological studies included studies of changes of the mean cellular volume of the nucleus/cytoplasm ratio, the density of the neuron and the gray/cell coefficient. The quantitative methods employed were those of Chalkley ('43 and .49). The qualitative morphological studies were carried out by means of microscopic examination of histological preparations. The chemical studies were concerned with determination of the content of the nucleic acid and phosphoproteins. The methods employed were those of Schmidet and Thannbauser ('45) and Allen ('40). A hypothetical succession of events taking place during the postnatal period of development of the cerebral cortex of the cat was outlined. The data obtained during the studies indicated that the morphological and chemical changes are determined by the age and body weight of the animals. The overall quantitative morphological changes during development were a decrease of neuron density, and of the nuclear/cytoplasmic ratio an increase of the mean cellular volume, of the nucleus/cytoplasm ratio and of the gray/cell coefficient. The qualitative morphological studies give evidence of the stage-by-stage occurring differentiation of the cortical layers and of the cells of the layers. The data of the chemical studies seem to indicate that the content of the phosphoproteins per gm of wet tissue is maintained at more or less constant level during the entire period of development and throughout the adult life. The content of PNA decreased during the fetal life but did not change significantly from the 1st day after birth to the adult stages, while the content of the DNA decreased during the prenatal period and after birth, and become stabilized only on the 11th day after birth. Further morphological and chemical studies developing and aging cerebral cortex of the cat are suggested.