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- 



Chorioid fissure 



Angulus prsethalamicus 



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 7^ weeks' human embryo. Aq. S., Aquaeductus 

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

 atum; H. b., tegmental swelling; R.'g., geniculate recess; R. /., recessus infundibuli; R.o., 

 recessus (prae-?) opticus; S.h., habenular evagination; S. M., sulcus hypothalamicus; S.p., 

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



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

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



Epithalamus (Corpus pineal' 



Metathalamus 

 (Corpora geniculaliO 



Corpora quadi isici 



Pedunculun ceiehri 



Cerebellum 

 ossa rhomboidea 



Medulla oblongata 



RhinencepUalon ,'' . 

 Pars opiica hypothalam 



Chiasma opticunr' ,'' 

 Hypophysis ' 



Pars maraillaris hjpothalami 



Pons [Varol 



FIG. 468. Brain of a human foetus in the 3d month, right half, seen from the left. His, SpaUeholz. 



mentioned constitute a metathalamic portion, while the portion derived from 

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



35 



