506 



TEXT-BOOK OF EMBRYOLOGY. 



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 

 Angulus prjethalamicu 



Foramen of Mon 



Ant. arcuate fissure 



Preterminal area 



Ant. olfact. lobe 



Olfactory nerve 



Post, olfact. lobe 



Hypothalamic region 

 Mammillary region 



Lamina terminalis 



FIG. 429. 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. 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 



Epitbalamus (Corpus p!ueale 



Met a thalamus 

 (Corpora geniculaia) 



Corpus striatum \ . 



Rhinenceplialon ^ 

 Pars optica hypothalami /' / 

 Chiasma opticum' y' 

 Hypophysis'' 



Pars maraillaris bypothalami* 



Pons [Varolfl- 



Corpora quadrigrmlna 



Pedunculus ceiebri 



Cerebellimi 

 Fossa rhomboidea 



Medulla oblongata 



FIG. 430. 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, 



