128 THE POCKET ANATOMY 



Boundaries : 



Roof. Floor. Laterally. 



Fornix. Lamina cinerea. Optic thalamus. 



Velum interpositum with Optic commissure. Peduncles of pineal 



choroid plexus of 3rd Tuber cinereum. gland, 



ventricle. Infundibulum. j^-u_j 



Corpora albicantia. Anteriorly. 



Posteriorly. Posterior perforated Pillars of fornix. 



Pineal gland. spot. Foramen of Monro. 



Posterior commissure. Tegmenta of crura Anterior commissure. 



Sylvian aqueduct. cerebri. 



Commissures : the anterior commissure will be described 

 with cerebral hemispheres. 



The posterior commissure : is a commissural layer of white 

 fibres connecting the two optic thalami posteriorly. It forms 

 the posterior boundary of the 3rd ventricle, being placed just 

 above the upper opening of the aqueduct of Sylvius, and 

 beneath the pineal body. 



The middle or soft commissure: a delicate band of grey 

 matter passing between the optic thalami, near middle of 

 ventricle. 



The optic thalami. Two oblong masses of grey matter, 

 covered with a thin layer of white fibres, the stratum zonale, 

 and projecting above into the lateral ventricles. 



Upper surface : there is a groove along this surface, running 

 from behind obliquely forwards and inwards, which corre- 

 sponds to the free lateral edge of the fornix and divides it 

 into two pear-shaped pieces, the outer (ventricular area) having 

 its base forwards and projecting in front, forming the anterior 

 tubercle, and the inner (extra- ventricular area) having its base 

 behind and to the inner side, which forms ihe posterior tubercle 

 or pulvinar. This surface is separated from the mesial, or 

 surface bounding the 3rd ventricle, by the peduncle of the 

 pineal body; and between this and the pulvinar is a trian- 

 gular depressed surface, the trigonum habenula. This surface 

 is partly covered by the fornix resting on the velum inter- 

 positum, and is separated externally from the caudate nucleus 

 by the taenia semicircularis. 



Posterior extremity is formed chiefly by the pulvinar. Below 

 and outside this is the eminence of the outer geniculate body ; 

 and just below this is the inner geniculate body, the brachium 

 from the superior corpus quadrigeminum passing between 

 them. 



Under surface : placed on the tegtnentum of the crus. 



External surface : fibres of the crusta (internal capsule) pass 

 between this surface and the lenticular nucleus,. 



