Growth of Human Nervous System. I. Growth of Cerebral Surface

Abstract

The interest in the extent and variability of the cortex of the human brain has led to a number of estimates of the surface area of the cerebrum (generally in the adult) by a variety of ingenious methods. 1 - 7 We have attempted to extend these studies by an experimental investigation of this area through a portion of the developmental period (from the fourth fetal or lunar month of prenatal life to 2 postnatal years) and in maturity. Our technique is described in detail in a forthcoming paper. 8 Briefly stated, the method consists of sectioning formalin fixed brains enclosed in a matrix with a mechanical device into slices 2 to 3.5 mm. in thickness. The area is then determined by measuring the outline of each section with a chartometer and multiplying the reading by the thickness of the section. The surface of the cerebrum is approximated by the sum of the values so obtained. Attempts to improve this technique by computing the sections as segments of cones and taking the means of their anterior and posterior outlines did not increase the accuracy of our determinations. Twenty cerebri were so studied. Figure 1 shows 10 of these drawn to scale (left lateral views) to illustrate the changes in size and form and in the configuration of the sulci in the series.

In measuring these structures figures were obtained for both “total” and “free” surface. “Total” surface indicates the entire cerebral surface including that portion buried in all of the cerebral fissures regardless of their depth. “Free” surface is a term used for the visible or external surface of the cerebrum only. In determining this value the chartometer was passed around the periphery of each section but only dipped into the lips of the sulci to the shallow point where their sides meet.