RELATIONS OF THE ADULT PINEAL ORGAN 415 



backward over the roof and lateral wall of the posterior horn and hinder 

 part of the inferior horn of the lateral ventricle ; in this situation they 

 form a thin lamina, the " tapetum," inside the fibres of the optic radiation. 

 The latter consist of afferent and efferent fibres which connect the lower 

 visual centres of the lateral geniculate body and superior colliculus with 

 the occipital cortex. It is said that no commissural fibres belonging to 



Fig. 279. — Transverse Section of Brain showing Relations of Pineal Body. 



Aq. S. : aqueduct of Sylvius. 



C.C. : corpus callosum. 



Ch. P. : choroid plexus. 



C.N. III. : third cranial nerve. 



F. : fornix, beneath which is the great 

 transverse fissure. 



H.M. : hippocampus major. 



I.C. : internal capsule. 



I.C.L.V. : inferior horn of lateral ven- 

 tricles. 



L.G.B. : lateral geniculate body. 



L.V. : lateral ventricle. 



the visual area of the cortex cross in the corpus callosum. So far as we 

 are aware, little is known about the function of the fibres of the tapetum 

 and the fibres of the forceps major which cross in the splenium of the 

 corpus callosum, and injury to these fibres does not appear to give rise 

 to any definite symptoms or disability. 



The under surface of the pineal body is typically separated from the 

 groove between the superior colliculi by a fold of pia mater, which forms 



M.G.B. : medial geniculate body. 



N.P. : nuclei pontis. 



O.M.N. : oculo-motor nucleus and 



medial longitudinal fascicle. 

 Op. T. : optic thalamus. 

 R.N. : red nucleus. 

 S.C. : superior colliculus. 

 S.C.P. : superior cerebellar peduncle 



(brachium conjunctivum). 

 S.N. : substantia nigra. 

 V.M.C. : vena magna cerebralis. 



