Tin: ORGANS or 1HI HI 



furrows that cut int.. li < the ren-bruin more or less deeply 



from the outside, btri cause no correspond rxud proje 



tin- wall of tin- ventricle. 



A ml> its Lfeni -ra 1 . the embryonic growth of the cerebral 



lea is e-pecially characterised by an nlar^em.-nt 1, . Jn 



the thii-il month tlio posterior loin- already coinj.l.-i.-ly overlies the 

 optic thalainus (til D tin- tifth month it begins to extend over 



the corpora qoadrigemi] :il>. which it, entirely covers up in 



the Mxih month. From there it spreads over the cerebellum 

 (fig. 25G). The cerebrum is not characterised in all .Mammals by 

 Mich an e\t raordinary growth as in Man; com; anatomy 



teache- lather that the stages of development of the In; in in 



ditlerent months h- il>ed, are met wit h in < 



permanent conditions. 



In some animals the itenor m:M_:i!i- oi the hemUph'-ivs extend as far a? 

 the corpora quadrigemina; in otlu-rs they cover th->e more or less compl- 

 in others, finally, they have irmwii o\er tlie i-ori-U-llum more or less. l. 

 whole, the increase in the volume of the cerebrum, which is so 

 Mammals, goes han<l in haml with an increase in int. 



\. -ides of the hemispheres undergo additional complica- 

 (in Man in the course of the second ami third month**), owing to 

 infoldings of their thin walls, which still enclo>e a large cavity. As 

 'ilt of this there arise on the outer >nrtace deep furrows, which 

 separate large areas from one another and which have been designated 

 as total furrows or fissures by His, who has riirhily r>iimated their 

 importance in the architecture of the brain. Corresponding to the 

 furrows which are visible on the outer surfai , there are more or less 

 prominent elevations on the inner surface of the lateral ventricles, 

 by means of which the latter become narrowed and reduced in size. 

 The total furrows of the cerebral hemispheres are the fissure of 

 SYLVIUS (fossa Sylvii), the arcuate ik-ure, embracing the hippo- 

 campal fissure (fissura hippocampi), the lis-ura h 

 calcarina, and the fissura parieto-occipitalis. The elections produced 

 by them are called the corpus striatum, foi nix and pes hippocampi, 

 tela choroidea and calcar avis. A prominence which in the embryo 

 corresponds to the lisMira parieto-occipitali-. becomes obliterated in 

 the adult by a considerable thickenini: of the \\all of the brain, so 

 that no permanent structure results from it. 



Thefasure of SYLVIUS (fig, _T)2 Sy.g) is the first one formed. It 

 appears as a shallow depression of the conrex outer surface at about 



