114 LABORATORY OUTLINE OF NEUROLOGY 



lentiform nucleus lying far laterally and the caudate nucleus 

 lying medially and projecting into the lateral ventricle, while 

 the internal capsule appears as a band of white fibers between 

 these two centers and between the lentiform nucleus and the 

 thalamus. In transverse and longitudinal sections of both the 

 sheep and the human brains identify the chief nuclei of the 

 thalamus (Herrick ('18), Fig. 79) and review the relations of 

 the various lemniscus systems to these centers (Herrick ('18), 

 Figs. 77 and 78) . The medial and anterior nuclei of the thala- 

 mus are seen to be clearly separate from the lateral group of 

 nuclei, including the lateral and ventral nuclei, the pulvinar 

 and the lateral and medial geniculate bodies. The lateral 

 group of nuclei constitute the "neothalamus," or new thalamus 

 and are sources of the thalamic radiations or sensory projection 

 fibers to the cortex. The medial and anterior nuclei belong to 

 the old thalamus and are concerned chiefly with intrinsic thal- 

 amic reflexes. Compare these structures as they appear in the 

 transverse sections with their appearance in the longitudinal 

 dissection of the left hemisphere. Try to build up in your 

 mind a three-dimensional picture of the fiber tracts in the 

 sheep's brain, as you have seen them in dissections and gross 

 sections. If microscopic sections through the thalamus and 

 corpus striatum are available, they should be studied in this 

 connection and the account given by Herrick ('18), Chap. X, 

 should be read. 



11. Optional Dissections of the Cerebrum 



141. The association tracts. The same specimen upon which 

 the dissections outlined in Sections 102 to 111 were made 

 can be used for the following dissections of the cerebrum. The 

 association tracts can be dissected out in great detail, following 

 the procedure directed for the sheep and human in Sections 119 

 and 120, working carefully with text-book diagrams and de- 

 scriptions of the chief systems in mind and teasing off the more 

 superficial systems before attempting to study the deeper sys- 

 tems. It will be found that the stronger and more easily 

 isolated association tracts do not connect the projection centers, 

 but the association centers. In view of the fact that in the 

 sheep the association centers are small when compared with 



