264 THE NERVOUS SYSTEM 



gyrus, are afferent fibers of the third order mediating sensations of touch, heat, 

 cold, and perhaps also pain as well as sensations from the muscles, joints, and 

 tendons (Head, 1918). These sensory fibers are located behind the corticospinal 

 tract in the posterior limb of the internal capsule. According to Wilson (1914) 

 the medullary laminae of the lentiform nucleus do not contain any thalamocor- 



tical fibers. 



The occipital stalk, or peduncle, is also known as the optic radiation and as 

 the radiatio occipitothalamica. Its fibers stream out of the pulvinar and lateral 

 geniculate body, pass through the retrolenticular part of the internal capsule, 

 and run in a curved course toward the occiput, around the lateral side of the 

 posterior horn of the lateral ventricle to the cortex of the occipital lobe, and es- 

 pecially to the region of the calcarine fissure (Figs. 190, 191). It also contains 

 some fibers arising in the occipital cortex and ending in the superior quadrigeminal 

 body. We have learned that it forms an important part of the visual path 

 (Fig. 162). 



Closely associated with the optic radiation in the retrolenticular part of the 

 internal capsule is the acoustic radiation (radiatio thalamotemporalis) . This 

 connects the medial geniculate body with the anterior transverse temporal gyrus 

 and the adjacent part of the superior temporal gyrus, and mediates auditory 

 sensations. It should be included as a part of the thalamic radiation. 



