642 PHYSIOLOGY. 



the posterior corpora quadrigemina, and thence by means of the 

 brachium posterioris of the corpora quadrigemina through the pos- 

 terior linib of the internal capsule to the first and second temporal 

 convolutions. It is made up mainly of auditory fibers. 



THE BRAIN. 



The weight of the brain is about fifty ounces, However, the 

 weight of the brain may be, as in the case of Cuvier, sixty-five 

 ounces. It is greater in civilized persons than in savage tribes; it 

 is likewise greater in the male than in the female; in an eminent 

 man than in an ordinary man. But what really shows the superiority 

 of the brain is not so much its enormous size nor the exuberance of 

 its convolutions, but the well-balanced development, the harmony, 

 of all of its parts. 



External Form. The brain is composed of two symmetrical 

 halves, or hemispheres. These are nearly entirely separated from one 

 another by the great longitudinal fissure. The parts which are intact 

 are located at the center and base and comprise the corpus callosum 

 and floor of the fourth ventricle. The surfaces of the hemispheres 

 are separated into lobes and convolutions by various fissures. The 

 convolutions appear to be infoldings of the gray matter of the brain 

 within its rigid confines, the cranial vault. The mode of spreading 

 of the fibers of the peduncle may have something to do with their 

 conformation also. The end obtained by their presence is to lodge 

 a much larger gray mass within a given space. 



There are five principal fissures in the brain : (1) the great longi- 

 tudinal; (2) the great transverse fissure between the cerebrum and 



Sylvian. 8y. p. asc., Ascending ramus of posterior limb, fi, Superior frontal. 

 J2, Inferior frontal, fa, Middle frontal. f 4 , Pararaesial frontal, d, Diagonal, 

 placed in this instance rather low down, and communicating with the Sylvian. 

 p.c. inf, Inferior precentral. p.c.i. ant., Its anterior ramus. p.c. sup., Superior 

 precentral. p.c.m, Mesial precentral. p.c. tr., Transverse precentral. rtc. tr., 

 Transverse retro-central, i.-p. inf, Intra-parietal, pars inferior (inferior post- 

 central), i.-p. sup., intraparietal, pars superior (superior postcentral). i.-p. 

 post. 8. hor., Intraparietal, pars posterior seu horizontalis. i.p. post., Intra- 

 parietal, pars posterior (parocoipital of Wilder), i.-p. pr. asc., An ascending 

 branch of the intraparietal. p.-o., Parieto-occipital. occ. ant., Anterior occipital. 

 occ. lat., Lateral occipital, calc., Posterior end of calcarine. ti, First temporal 

 or parallel, t^ asc., Its posterior ascending extremity, detached, iz. Second tem- 

 poral, tz asc., Its posterior ascending extremity joined to and apparently con- 

 tinuous with the first temporal. 



Gyri 7* 1 ,, F 2 , F 3t First, second, and third (superior, middle, and inferior.) 

 frontal, a, Posterior part of third frontal. 6, Middle part (pars triangularis). 

 c. Orbital part. AF., Ascending frontal. A. P., Ascending parietal. T lt T 2 , T s , 

 First, second, and third temporal. 







