THE NERVOUS SYSTEM. 



543 



between these two structures. There can, then, be distinguished in the dien- 

 cephalon three regions, a hypothalamic region, as already described, an epithala- 



Hippocampal 

 fissure 



Chorioid fissure 



Anguluspraethalamicus 



Foramen of Monro- 



Ant. arcuate fissure 



Preterminal area 



Ant. olfact. lobe 



Olfactory nerve 



Post, olfact. lobe 



Hypothalamic region 

 Mammillary region 



Lamina terminalis 



R.o. Hypophysis 



Fig. 467. — Median sagittal section of the brain of a ji weeks' human embryo. Aq. S., Aquasductus 

 Sylvii; C. c, fold between mid- and interbrain; C.m.j commissura mollis; C. s., corpus stri- 

 atum; H. b.j tegmental swelling; R.g., geniculate recess; R. i. } recessus infundibuli; R. 0., 

 recessus (prse-?) opticus; 5. h., habenular evagination; S. M. t sulcus hypothal amicus; S.p., 

 pineal evagination; T. J 1 ., thalamus. His. 



mic region comprising the pineal body, ganglia habenulse and related structures, 

 and finally the thalamus proper. In the latter, the geniculate bodies already 



Epithalamus (Corpus pineaJe; 



Met a thalamus 

 (Corpora geniculaial 



Corpora quadngf inin 



Corpus striatum 



• Pcdunculua cerebri 



Rhineneeplialon / / t 

 Pars optica hypothalami / / 

 Chiasm a opticuni .' 

 Hypophysis'' 



Pars Diamiltaris hypothalami* 



Pons [Varolii 



Cerebellum 

 Fossa rhomboidea 



Medulla oblongata 



Medulla; 

 /spirtalj s 



Fig. 468.— Brain of a human foetus in the 3d month, right half, seen from the left. His, Spalteholz. 



mentioned constitute a metathalamic portion, while the portion derived from 

 the thickened part, which is continuous anteriorly with the corpus striatum, 

 35 



