112 ANTHROPOLOGY. 



scale : ', dura mater ; ", ligamentum dentatum ; ', anterior root of a spinal 

 nerve cut away ; ', do, entire ; ', a posterior root, with the ganglion ; ', ante- 

 rior, ', lateral furrow. Fig. 5, spinal marrow from behind : ', posterior 

 longitudinal furrow ; *, calamus scriptorum ; ", posterior column ; \ its 

 division by a furrow into halves. Figs. 9, 10, 11, cross sections of the spinal 

 marrow beneath the medulla oblongata. 



C. The Encephalon. 



The term encephalon is conveniently employed to denote the portion of 

 tiie cerebro-spinal axis which is contained within the cavity of the cranium. 

 Before proceeding to the description of the individual portions of the ence- 

 phalon, it will be proper to premise some general considerations, borrowed 

 from Tiedemann, having reference to its entire mass. 



The average Aveight of the human brain amounts to about 48 ounces for 

 the male, and 44 ounces for the female. The brain of men who have been 

 «listinguished for their intellectual attainments has often been found to exhi- 

 bit a large size. That of Cuvier weighed 3 lbs., 11 oz., 4 dr., 40 gr. On 

 the other hand, the brain of an idiot, fifty years old, weighed but 1 lb., 8 oz., 

 and 4 dr. 



The brain attains its full size, on an average, about the seventh or eighth 

 year. 



The brain of the new-born child is. relatively to the size of its body, the 

 largest. The proportion is as 1 : 6. It decreases in proportion as man 

 attains his full growth. Thus, in the second year the proportion of the 

 brain to the body is as 1 : 14; in the third, 1 : 18 ; in the fifteenth, 1 : 24. 



Although the female brain is absolutely smaller than the male, yet rela- 

 lively to the size of the body it is usually larger. 



1. Surface of the Enx'ephalon. The brain, in horizontal projection, is 

 seen to be of oval shape, the smaller end of which is directed forwards. 

 The superior and lateral surfaces are convex, and have a smooth appear- 

 ance, from the visceral layer of arachnoid being spread over them. When 

 the membranes have been removed, the surface of the brain is seen to be 

 impressed with numerous convolutions. 



The superior surface is divided along the median plane into two equal 

 and nearly symmetrical portions by a vertical fissure, which receives the 

 great falx of the dura mater. In front and behind, this fissure completely 

 divides the central lobes. In the middle, the fissure is interrupted by a hori- 

 zontal lamina of white fibres, called the corpus callosum^ the great commis- 

 sure of the cerebral hemisphere. The inferior surface of the brain presents 

 three segments each on a different plane, and corresponding with the three 

 ibssae of the cranium. The anterior segment, and the one on the highest 

 level, correspond to the anterior fossa of the cranium, and rest upon the 

 foofs of the orbits. The continuation of the anterior median fissure sepa- 

 rates its right and left portions, this distinction being rendered more com- 

 plete by the attachment of the falx to the crista galli of the ethmoid. In 

 a distinct sulcus, parallel to and immediately on each side of the longitudinal 

 lissure, we find the olfactory process or nerve. A curved fissure of con- 

 818 



