78 



PSYCHOBIOLOGY 



medial and coronal planes are designated horizontal planes. (See Cun- 

 ningham, Anatomy, Introduction.) 



The spinal cord [Figs. 29, 37] extends from about the 'small' of the 

 back into the skull, where it ends, at about the level of the ears, in the 

 enlargement called the medulla oblongata (or myelencephalon), [Figs. 

 65-70], which is about an inch in length. Above the medulla on the front 

 is a fibrous band, the pons, running horizontally across and into the 

 cerebellum, which lies above and behind the medulla. (Pons and cere- 

 bellum together constitute the metencephalon). These are the three divis- 

 ions of the hind-brain (or rhombencephalon). 



Above the medulla and continuous with it is the mid-brain (or mesen- 

 cephalon), about three quarters of an inch in length, on the back of which 

 are the protuberances known as the corpora quadrigemina, and on the 



Kissura transversa cerebri 

 Aquacductos cerebri (Sylvii) 

 Lamina quadrigemina 

 Velum medullar e 

 anterios 

 Ventrical us 

 quarrus 



Ventriculns tertius 



Tela chorioidea ventricttli lertii_ 

 Corpus pineale, 



Mass* intermedia 



Foramen interventriculare (Monroi) 

 Column a fornicis 



Septum pellucidora 



Lamina rostralj* 



Vcrfcii 



Arbor *itae 



Corpus roedullare ccreoelli '' 



Medulla oblongata 



\ Tuber cincreum 

 Corpus mamillarc 



Pons (Varoli) 



Commissura anterior 

 " - Lamina terminalis 

 ■* Chiasms opticum 

 Infundibulum 

 V Hypophysis 



Fig. 66. Medial sagittal cross-section of brain, showing medial surface of left 

 hemisphere, one-half normal size. (Toldt, Anatomiscker Atlas.) 



front the beginning of division into right and left portions, the crura 

 (singular eras). This division becomes complete in the diencephalon, 

 forming the two thalami, upon which are superposed the corpora striata 

 [Fig. 70]. From the upper part of the thalami grow the cerebral hemis- 

 pheres or cerebri (or telencephalon), which are the largest and most 

 conspicuous parts of the brain, folding over and concealing nearly all of 

 the mid-brain. Diencephalon and telencephalon together constitute the 

 fore-brain (or prosencephalon) [Fig. 28]. 



