About the Asymmetry of Human Brain

Abstract

On 500 macerated and gradually decreased human skulls, by measuring the oblique diameters, I determined the type of skull. On 300 specially conserved brains, I examined the appearance of outer and inner structures of symmetrical and asymmetrical brains.

On 220 skulls (4496), I established occipital symmetry. In 184 cases (36,8%), I found the left occipitopetalia joined with temporoparietopetalia of the right or left side, while in some cases also with frontopetalia.

The third group of cases with occipitopetalia on the right side, I ascertained in 96 cases (19.2%). In addition to that, the above-mentioned cases can be characterized by temporoparietopetalia and frontopetalia of the opposite side or the same side.

I have examined the appearance of brain in relation to configuration of man's skull on 300 specially conserved brains in 10 and 5% formalin. Brain is conserved in its own calvaria. Before extracting brain from skull, I determined its type by measuring oblique diameters. On the brain I examined the appearance of the outer configuration as well as topological morphology of separate parts of symmetrical and asymmetrical brains. On horizontal and frontal cross section of brain made on certain planes as well as on specially prepared. I examined the appearance of inner structures of symmetrical and asymmetrical brains. Each cross section and specially prepared were photographed, so that it was possible to examine topological morphology by comparing the appearance of right and left hemisphere. On the side of the occipitopetalia cerebral parts are retroposed, while on side of temporoparietopetalia and frontopetalia they are latero- and antero displaced.

Appearance of middle skull fossa is of great importance in forming skull base. The appearance of middle skull fossa is primarily influenced by the following factors: asymmetric growth of temporal lobes of brain, rotation of pyramids of temporal bones and withdrawal of pyramids by the tentorium cerebelli.

With its asymmetry, the cerebrum follows the skull asymmetry. However, it seems to me that pyramid rotations and uneven growth of temporal lobes of the brain are very significant in forming the asymmetry of skull and brain. Besides the above mentioned, the following also participate in the formation of skull and brain asymmetry: tentorium cerebelli, asymmetry in development of desmo and chondrocranium as well as powers which act in direction of alae minores of the sphenoid bone and cristae occipitales internae. Certainly, the erect position of man and angulation of skull base effect the formation of neurocranium and brain asymmetry.