THE NERVES. 365 



size of a pea, externally white, internally gray, (in the foetus, one 

 only,) separated by a fissure, united by means of gray matter ; 

 they form the extremities of the anterior, descending crura of the 

 for nix. 



6. Tuber cinereum, a gray, soft mass in the triangular space 

 between (and before) the corp. mamillar. and tracti optici, the floor 

 of the third ventricle; above it lies the commissura anterior ; 

 under it the 



7. Infundibulum, a reddish, hollow body, directed obliquely 

 forwards, two lines long, to which 



8. Hypophysis (s. glandula pituitaria) is attached. It consists 

 of an anterior larger and whiter, and a posterior smaller and 

 yellowish lobule, lies in the seUa turcica, is very vascular, and 

 weighs from five to ten grains ; on its sides the plexus caver- 

 nosi. In the foetus and the lower animals hollow. 



9. Tractus nervorum opticorum, two white, flat bands, fifteen 

 lines long, arising behind from thalamus opticus and corp. genicu- 

 latum ; they wind around the crura cerebri on the outside and be- 

 hind, at the place where they enter into the brain, then pass, on the 

 outer side of tuber cinereum, inwards and forwards, and unite be- 

 fore the tuber cinereum. 



10. Chiasma nervorum opticorum, a quadrangular flattened 

 ganglion, the internal fibres of which decussate, while the external 

 pass directly forwards ; it lies before the hypophysis, behind the 

 lamina cribrosa. Its anterior border is united, by means of a 

 vertical lamina terminalis, with the anterior commissure, which is 

 situated above it. From this the optic nerves pass off. 



1 1 . Lamina cribrosa cerebri s. substantia perforata anterior, a 

 thin, white plate before the chiasma, perforated by many vessels, 

 bounded in front by the commencement of corp. callosum. From 

 it the olfactory nerves arise. 



619. II. The Azygos Parts in the centre of the Cerebrum. 



1. Corpus callosum s. commissura maxima, a white flat band, 

 three and a half inches long, eight to ten lines broad, and two to 

 three thick, in the centre between the great hemispheres (one inch 

 distant from their anterior, two from their posterior border), visible 

 from above in the deep longitudinal fissure, consisting of transverse 

 fibres (strice transversce Willisii). Its superior arched surface 

 presents two longitudinal strice (strict longitudinaks Lancisii), 

 between which a slight depression is found (raphe) ; upon it the 

 artt. calloscs and the free border offalx cerebri are situated. Its 



