110 LABORATORY OUTLINE OF NEUROLOGY 



specimen can profitably be used for a repetition of the dissection, 

 or it may be cut into a series of transverse or longitudinal 

 slices, in each of which some of the structures already observed 

 may be identified. 



Some members of the class may slice this hemisphere in the 

 transverse plane, others in the horizontal, and others in the 

 sagittal, and these specimens may be compared by all members. 

 Compare these sections with transverse sections of the human 

 brain to be supplied by the instructor. Poorly preserved brains 

 which are of small value for dissection by the method of teasing 

 will give excellent gross sections for this study. In these 

 sections look particularly for the continuation of the cerebral 

 peduncle into the internal capsule. Make an especial study of 

 the relations of the internal capsule to the adjacent structures, 

 noting how the corpus striatum is made up of the 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 

 ('15), Fig. 79) and review the relations of the various lemniscus 

 systems to these centers (Herrick ('15), Figs. 77 and 78). The 

 medial and anterior nuclei of the thalamus 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 thalamic reflexes. Compare 

 these structures as the}' appear in the transverse sections with 

 their appearance in the longitudinal dissection of the left hemi- 

 sphere. 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 ('15), Chap. X, should be read. 



