THE NERVOUS SYSTEM. 



543 



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

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



Hippocampal 

 fissure 



Chorioid fissure 

 Angulus praethalamicus 



Foramen of Mon: 



Ant. arcuate fissur 



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 75 weeks' human embryo. Aq. S., Aquasductus 

 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.i., recessus infundibuli; R.o., 

 recessus (prae-?) opticus; S. h., habenular evagination; 5. 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 



Corpus stnaiiin 



Epithalamus (Corpus pinealej 



Metathalainus 

 (Corpora geniculaia) 



Corpora quadrixnui 



'Pedunculus, cejebri 



RhinencepUalon / .- 

 Pars optica hypothalami /' 

 chinsiua opticum' .' 

 Hypophysis ' 



Pars maraillaris bypothalami" 

 Pens [Varo 



Cerebellum 

 -.-Fossa rhomboidea 



Medulla oblongata 



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 



