^o6 



NA TURE 



[Feb, 19, 1874 



and each shaped somewhat like a life preserver. These 

 are the '• olfadoiy lobes," and from the swollen head of 

 each proceed the delicate nerves of smell. 



2. An enormous pair of folded masses which form the 

 great bulk of the human brain and are called the cerebral 

 lobes or hemispheres. These are so large and prepon- 

 derant in man, as to hide every other part of the human 

 brain when that organ is viewed from above. 



3. A relatively very small portion, but one easily recog- 



On turning to the brain of the frog from that of man it 

 is at first sight difficult to find out the resemblances, and 

 to determine which portions of the one answer to definite 

 regions of the other. 



Fig. 63. — The Brain as seen when a Vertical Longitudln;iI Section has been 

 made through its imidile. Av, arbor vita; or the cerebeUum : c, cere- 

 brum : cc, corpus c .llosum ; cq, corpora quadngemina ; f fornix (be- 

 tween the fornix and the corpus callosum is the septum lucidum) ; ;«, 

 meouUa oblongati : ma, corpus mammillare ; on, optic nerve ; //, pineal 

 gland; pt, pituitary body ; /7', pons Varolii; x. soft, or middle com- 

 missure. 



nised since it supports two conspicuous little bodies. One 

 of these (Figs. 69, 70, 71,//) is called the puieal ^land, and 

 projects more or less upwards ; the other (Figs. 69, 70, 71, 

 pf) projects downwards and is called \^q. pituitary body. 



4. An also ver\' small portion relatively, is d istinguished 

 by bearing certain small prominences (Fig. 69, cq^ and Fig. 

 70, na and te) placed behind the pineal gland, and called 

 corpora quad) igeiniiia. 



5. A rounded mass of finely folded brain-substance, 

 placed at the lower part of the back of the head beneath 

 the hinder portion of the cerebral hemispheres. This is 



Fig. 70. — Enlarged and Dldgramniatic View of a VerticAl Sec 

 through the Corpus Callosum and the part-. ijJort'. ar, ar 

 missure ; cc, corpus callosum ; chl, cerebellum ; tv«, corpus mammillare ; 

 f^ fornix ; fni, foramen of Monro ; z, infundibulum ; Ip, locus ; perfora- 

 tus medius; mo, medulla oblongata ; na, nates ; on, optic nerve ; /c, 

 posterior commissure ; /?', pons Varolii ; //. pmeal gland ; pt^ pituitary 

 iDody ; s, soft, or middle commissure ; si, septum lucidum ; t, lamina 

 terminalis; ie, testes; ■:•, velum interpositum(between it and the fornix is 

 a space enclosed bv the folding over of the cerebrum upon the roof of 

 the third ventricle) ; 3, upper, and 3', lower part of third ventricle ; 

 4. fourth ventricle— between them is the iter a tertio ad qrtarium ven- 



called the cerebellum^ and when cut through exhibits sin- 

 gular, radiating, tree-like markings, due to the infoldings 

 of the surface of the organ, and called ^^ arbor vita (Fig. 

 70, av). 



6. That part which directly continues the brain into the 

 spinal marrow (Fig. 71, ;;/). It is overlapped by the cere- 

 bellum, and contains that portion of the remnant of the 

 primitive nervous canal, wliich is named tht fourth ven- 

 tricle. This sixth fundamental part of man's brain is 

 called the medulla oblongata. 



Fig. 71. — Diagram illustrating the progressive Changes that take place 

 during successive stages of the Development of the Brain. 1. The 

 brain in its very early condition, when it consists of three hollow vesicles 

 the cavity of which is continuous with the wide cavity id) of the primi- 

 tive spinal marrow {;«). The brain substance forms an envelope of 

 nearly equal thickness throughout. 2. Here the firs', vesicle or fore- 

 brain has developed the pineal gland (//) above and the pituitary body, 

 ipt) below. The wall at the anterior end of the lirst vesicle (or fore- 

 brain) is the lamina terminalis (/t. 3. This figure shows the cerebrum 

 {cr] budding from the first vesicle, its anterior part {p) being prolonged 

 as the olfactory lobe (the so-called olfactory nerve), the cavity of the 

 cerebrum (or incipient lateral ventricle) communicating with that of the 

 olfactory lobe in front and with that of the first cerebral vesicle (third 

 ventricle) behind. The latter communication takes place through the 

 foramen of Monro. The walls of the three primitive vesicles are be- 

 coming of unequal thickness, and the cavity t^) of the middle vesicle 

 {iter a tertio ad gtiartutft ventricuhaii) is becoming reduced in relative 

 size 4. The cerebrum is here enlarged, and the inequality in thickness 

 of the wall of the primitive vesicle is increased- The thickened upper 

 part of the wall of the cerebrum is the fornix (/"). 5. This figure shows 

 the cerebrum still more enlarged, and with a triradiate cavity [/, i, 2, 

 3). The fornix has now come to look slightly downwards ; doited lines 

 indicate the downward extension of its anterior part, into the corpora 

 mammillaria. 6. Here the cerebrum is still more enlarged and back- 

 wardly extended The fornix Ls shown bordering the descending cornu 

 and extending into the temporal lobe {tl) of the cerebrum, which lobe is 

 destined to descend (when the brain is fully developed) so much 

 more that it comes to advance forwards. The fornix borders the mar- 

 gin of the very thin outer wall of the descending cornu, which when 

 torn forms the fissure of Bichat. The bending back of the cerebrum has 

 now almost enclosed (between the fornix and the velum) the space (-r) 

 which in Fig. 4 is widely open, making what is morphologically called, 

 the outside of the brain come practically to be in its very centre, a, 

 fore-brain ; b, mid-brain ; c, hind-brain ; cb, cerebellum ; cr, cerebrum ; 

 d^ cavity of the medulla './^ fornix ; /, lateral ventricle ; ;«, medulla ob- 

 longata ; fna, corpora mammillaria ; o, olfactory lobe ; /, pons Varolii ; 

 Pl, pineal gland ; //, pituitary body ; g, corpora quadrigemina ; r, crura 

 cerebri ; t, lamina terminalis ; tl, temporal lobe of the cerebrum ; .v, 

 space, enclosed by the extension backwards of the cerebrum ; i, anterior 

 cornu of lateral ventricle ; a, its middle or descending cornu ; 3, its pos- 



In the earliest conditions of the human brain there- 

 semblance is much more marked and obvious ; it is later 



