316 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



pulvinar. The lateral surface is in contact with the internal 

 capsule. 



The Connections of the Thalamus. The thalamus is a gan- 

 glion interposed between the sensor tracts in the legmen turn 

 and the cerebral cortex as well as an important link in the 

 optic radiation path. Also motor tracts concerned with instinc- 

 tive movements of an emotional nature. It is a relay station 

 for the various tracts which convey sensations of touch, tem- 

 perature, and pain from the body, extremities, head and neck, 

 of muscle sense, and of the special senses. It transmits these 

 to and receives in turn impulses from the cerebral cortex. As 

 an "emotional" centre it is also under the inhibitory influence 

 of the cerebral cortex, which, if the emotion be not too strong, 

 prevents its external manifestation. (Gray.) 



The pineal body is small, reddish-gray in color, found 

 between the caudal ends of the thalami, and occupying the 

 depression between the two superior corpora quadrigeminal 

 bodies. Above is the velum interpositum, which intervenes 

 between it and the splenium of the corpus callosum. Its 

 attached base is a hollow peduncle divided into a ventral and 

 dorsal stalk by the intrusion of the epiphyseal recess of the 

 third ventricle. The dorsal stalk continues on either side and 

 upon both thalami as the stria medullaris; it is also reinforced 

 by fibers joining the habenulae of the two sides; it is some- 

 times called the habenular commissure. The ventral stalk is 

 folded over the posterior commissure. 



The external geniculate body, or pregeniculum, are found on 

 the inferior anil external aspect of the thalamus and its posterior 

 extremity the pulvinar. They contain fibers which are 

 received in front from the outer division of the optic tract, 

 and behind connect with the superior quadrigeminal bodies 

 through the prebrachium; other fibers end in the thalamus. 



(NOTE. The external and internal geniculate bodies are 

 generally included under the head of metathalamus.) 



The nidus, or ganglion habenulae, is placed in the depression 

 (the trigonum habenulae) between the pineal body and the 

 caudal end of the thalamus. They are in relation with each 

 other through the habenular commissure, which Js connected 

 with the dorsal stalk of the pineal body. 



The posterior commissure is a white band of fibers crossing 

 from side to side in the ventral stalk of the pineal body, bridg- 



