'/'///; THALAMUS 



S25 



Both the structures of the nietathalamus, the lateral and medial geniculate 



bodies, arc connected with the optic tract. As this tract curves around the cerebral 

 peduncle it divides into two main routs. The lnl< ml <j< in/'ii/<//< Imi/i/ receives a I a re- 

 port ion of (lie libres of the lateral root of the optic tract: the remainder pa under 

 tliis body and enter the pulvinar of the thalamus. The medial geniculate body is 

 connected with the medial root of the optic tract, which root consists largely, not 

 of retinal fibres, as does the lateral root, but of the fibres forming Guddcn's com- 

 missure (the inferior cerebral commissure). 



Of the epithalamus, the epiphysis (pineal body, conarium) is the most con- 

 spicuous external feature. This is an unpaired, cone-shaped structure, about 7 

 mm. Ions and 4 mm. broad, which also projects upon the mesencephalon so that 

 its body rests in the groove between the superior quadrigeminate bodies. Its stem 



I'M,. 614. DISSECTION OF BRAIN SHOWING: MKTVTIIAI. AMI'S AND PULVINAR WITH ADJACENT 



STBUCTTTRKS. 



I'.tr/'.lTE NUCLEUS 



II:I:MIXALIS 



ITI.riX.IK 

 Ill-Tic TRACT 



r.i /;/.'/',/:'//- 

 \ i //; UODY 



M Kill A I. HKXH'U- 

 LATK IHIIIY 



LATKV. II. './ 



/,.i //; BODY 

 CORPUS 



.V.I MM II. I. I AT 



nrrii- 77/HT 

 /..i /7.7.M/, >//./.! i- 

 OLl-'Ai'TnltY Ti:.li''l' 



OLFACTORY BULB 



ixsl LA (central Me} 

 CAI'HA or r.i I - 



DATE HVCLSV8 



AXTKRKll: 

 ///./ <II:A TED 

 SUBSTAXi'K 



is attached in the mid-line at the posterior extremity of the third ventricle, and there- 

 fore just above the posterior commissure of the cerebrum (fig. 607). It is covered 

 by pia mater, ami is enclosed in a continuation of the tela chorioidea of the third ven- 

 tricle. Though it developes as a divert iculum of that portion of the anterior primary 

 vesicle which gives origin to the thalamencephalon, it is wholly a non-nervous struc- 

 ture, other than the sympathetic fibres which enter it for the supply of its blood- 

 vessels. 



It consists of a dense capsule c ,f libmus tissue (pia muter) from which numerous septa 

 inwards, dividing the inli-rior into a number of intercommunicating compartments filled with 



cpii liclial (ependymal) cells of the same origin a^ the ependyma lining the ventricles and aqueduct 

 below. Among these cells are frei|uently found small accretions (brain-sand, acerviilu- i-erebri), 

 consisting of mixed pho-phatc.- of lime, magnesia, and ammonia and carbonates of lime. The 

 compartment,- form a closed system. In function the epiphysis ranks as one of the glands 

 of internal secretion of the body, and it is often referred to as the 'pineal gland.' 



Apparently arising from the base of the epiphysis. but having practically nothing 

 to do with it, are the striae medullares of the thalamus (striie pineales, pedunculi 



