THE STRUCTURE OF THE BRAIN STEM 



423 



strand of white fibres connecting the anterior parts of the two optic 

 thalami and known as the anterior commissure. The roof of the 

 third ventricle is formed entirely of epithelium, the ependyma, along 

 the upper surface of which is the layer of pia mater, the velum inter- 



('nrplis rallnMin. 



Lateral ventricle' 



Nucleus caudatus 



Internal capsule 1 



Thalamib 



Nucleus Icntiformir 



Anterior eomniis-, 

 sure 



Colliculus superior 

 Inferior brachium 



Colliculus inferior 

 4th nei v 



Trigonum lenmisci 

 5th nerve 



Brachium con- 

 junct ivum 



Pons 



8th nerve 



Restiform body 



9th nerve 



10th ner\e 



Olive 



3rd nerve 

 Corpus niamniillare 



FIG. 190. 



Olfactory tract 

 Trigonum olfac. 



Optic nerve 

 Ant. perforated space 

 Optic tract 



th nerve 



12th nene 



Right lateral aspect of brain stem, with a part of the 

 cerebrum. (J. SYMINGON.) 



positum. The roof is invaginated into the cavity by two delicate 

 vascular fringes, the choroid plexuses. At the back part of the roof is 

 attached the stalk of the pineal body, and behind this stalk, between 

 the anterior parts of the anterior corpora quadrigemina, is a small 

 space known as the trigonum liabenulce, which contains a well-marked 

 collection of nerve-cells known as the ganglion habenulce. The lateral 

 walls are formed entirely by the optic thalami. The upper surface of 

 the optic thalamus looks into the lateral ventricle of the cerebral 



