A LABORATORY OUTLINE OF NEURO-ANATOMY 371 



the corpus callosum can be determied by examination of the medial aspect of the right 

 half of the sheep's brain. As the sections are removed note the relation of the gray 

 and white matter (Fig. 175). Gently press apart the two hemispheres and note the corpus 

 callosum at the bottom of the longitudinal fissure. Now with a blunt instrument 

 dissect away the gray and white matter from the dorsal surface of the corpus callosum 

 (Fig. 175). Be careful not to injure a thin layer of gray matter, the indusium griseum, 

 which covers this surface. Study the corpus callosum in this specimen and in the median 

 sagittal sections of the sheep and human brains (Figs. 158, 159, 175; pp. 243-245). 

 Examine the septum pellucidum in the median sagittal sections. 



104. The Lateral Ventricles (pp. 246-251). Cut through the corpus callosum of the 

 sheep's brain as indicated in Fig. 178, leaving a median strip in position. Make a 

 careful examination of all the parts thus exposed, including the septum pellucidum. 

 On the right side of the specimen expose the entire extent of the inferior horn of the 

 lateral ventricle by freely cutting away the lateral portion of the hemisphere as indicated 

 in Fig. 182. Remove the caudate nucleus to demonstrate the entire extent of the ante- 

 rior horn, and finally demonstrate the continuity of the lateral ventricle with the cavity 

 of the olfactory bulb (Fig. 182). Now study the lateral ventricle and the structures 

 which form its walls as these are illustrated on the two sides of this specimen. Note 

 the chorioid plexus (Fig. 183) and chorioid fissure. 



105. Study the lateral ventricle as seen in the frontal sections of the left hemi- 

 sphere of the human brain (Figs. 186-189). It has an additional part, the posterior 

 horn, not seen in the sheep. Endeavor to reconstruct a mental picture of its shape 

 (Fig. 176). 



106. The Corpus Striatum (pp. 253-257). Examine again the caudate nucleus as 

 it bulges into the lateral ventricle (Fig. 178). Take the right lateral half of the sheep's 

 brain and make a horizontal section through the cerebral hemisphere, passing through 

 the lower border of the genu of the corpus callosum and the lower border of the habenular 

 trigone. Locate the lentiform and caudate nuclei, the claustrum, and the internal 

 and external capsules (Fig. 192). 



107. Dissection of the Lentiform Nucleus and the Internal Capsule. On the left 

 side of the sheep's brain, in which the lateral ventricles have been exposed, remove the 

 cortex and white matter superficial to the lentiform nucleus. Begin by grasping with 

 tissue forceps the olfactory bulb close to its peduncle and tear it away, pulling in a 

 lateral and caudal direction. There should come away with it the superficial part of 

 the anterior perforated substance and part of the lateral olfactory gyrus (Fig. 83). 

 This will expose the ventral part of the lentiform nucleus, and the structures lateral 

 to that nucleus can now be removed. With a blunt dissecting instrument scrape away 

 everything superficial to the lentiform nucleus and continue the dissection until the 

 nucleus and the corona radiata are fully exposed (Fig. 87). Now scrape away the 

 lentiform nucleus and expose the internal capsule (Fig. 260). In removing the nucleus 

 you can obtain a clear idea of its shape and size. 



108. Dissection of the Internal Capsule. In the same specimen remove the optic 

 tract and trace the basis pedunculi into the internal capsule and follow the fibers from 

 the internal capsule into the corona radiata. Trace the optic radiation from the poste- 

 rior extremity of the internal capsule to the cortex near the occipital pole (Fig. 260). 



109. Dissection of the Caudate Nucleus. On the left side of the same sheep's 



