

1PHALON 



the cells of the thalamus form four principal groups or stalks : (a) those of the ante- 

 rior stalk pass through the frontal part of the internal capsule to the frontal lobe ; 

 (6) the fibers of the posterior stalk (optic radiations) arise in the pulvinar and are 

 conveyed through the occipital part of the internal capsule to the occipital lobe; (c) 

 the fibers of the inferior stalk leave the under and medial surfaces of the thalamus, 

 and pass beneath the lentiform nucleus to the temporal lobe and insula; (d) those 

 of the parietal stalk pass from the lateral nucleus of the thalamus to the parietal 

 lobe. Fibers also extend from, the thalamus into the corpus striatum those 

 destined for the caudate nucleus leave the lateral surface, and those for the lenti- 

 form nucleus, the inferior surface of the thalamus. 



Superior brachium Lateral geniculate body 

 Inferior brachium \ I Medial geniculate body 



Pulvinar 

 Pinearbody \ 



Optic tract 



Superior collicul 

 Inferior collicul 



Frenulum veli 



Trochlear nerve 



Lateral lemniscus 



Superior peduncle 



Middle peduncle- 

 Rhomboid fossa 



Optic commissure 



Oculomotor nerve 



'rigeminal nerve 



Acoustic nerve 

 facial nerve 



Abducent nerve 



Hypoylossal nerve 



Accessory nerve 



Fib. 719. Hind- and mid-braina; postero-lateral view. 



The TYletathalamus (Fig. 719) comprises the geniculate bodies, which are two in 

 number a medial and a lateral on each side. 



The medial geniculate body (corpus geniculatum mediate; internal geniculate body; 

 postgeniculatwii) lies under cover of the pulvinar of the thalamus and on the lateral 

 aspect of the corpora quadrigemina. Oval in shape, with its long axis directed 

 forward and lateralward, it is lighter in color and smaller in size than the lateral. 

 The inferior brachium from the inferior colliculus disappears under cover of it 

 while from its lateral extremity a strand of fibers passes to join the optic tract. 

 Entering it are many acoustic fibers from the lateral lemniscus. The medial 

 geniculate bodies are connected with one another by the commissure of Gudden, 

 which passes through the posterior part of the optic chiasma. 



The lateral geniculate body (corpus geniculatum laterale; external geniculate body; 

 pregeniculatum) is an oval elevation on the lateral part of the posterior end of the 

 thalamus, and is connected with the superior colliculus by the superior brachium. 

 It is of a dark color, and presents a laminated arrangement consisting of alternate 

 layers of gray and white substance. It receives numerous fibers from the optic 

 tract, while other fibers of this tract pass over or through it into the pulvinar. 

 Its cells are large and pigmented; their axons pass to the visual area in the occipital 

 part of the cerebral cortex. 



