108 LABORATORY OUTLINE OF NEUROLOGY 



134. Now pulling carefully so as to tear the tissue slightly, 

 draw away the ventricular wall along the upper border of the 

 caudate nucleus. The internal capsule fibers can now be seen 

 passing downward and backward, lateral to the caudate nucleus. 

 By teasing away the remaining association fibers on the lateral 

 side of the hemisphere the lentiform nucleus (a large gray mass) 

 will be exposed to view and the internal capsule fibers will be 

 seen passing downward and posteriorly between the caudate 

 and lentiform nuclei. By teasing away the gray cell masses 

 of the lentiform nucleus some of the fiber bundles can be seen 

 passing into the cerebral peduncle (pedunculus cerebri). Care 

 must be taken not to dissect too deeply and thus injure the 

 underlying thalamus, which lies medially of the posterior part 

 of the internal capsule (cf. Burkholder ('12), Plate XXII). 



135. Retina. — If microscopic preparations are available, study 

 the histological structure of the retina. From the reference 

 books master the arrangements of its neurons and the course of 

 nervous impulses within it. See Bailey ('16), pp. 561-565; 

 Barker ('01), Chap. XXXVII, pp. 532-543; Cunningham ('15), 

 pp. 814-818; Herrick ('15), Figs. 97-99; Howell ('15), Chap. 

 XVIII, pp. 336-367. 



136. Optic system. — In the sheep dissection remove the hippo- 

 campus. Identify the structures on the lateral surface of the 

 thalamus and midbrain: pulvinar, lateral and medial geniculate 

 bodies, superior and inferior colliculi. Follow the optic tract 

 from the chiasma to the thalamic optic centers (pulvinar and 

 lateral geniculate body), where the thalamic optic fibers ter- 

 minate. Trace other fibers of the optic tract over the surface 

 of the medial geniculate body to the superior colliculus of the 

 midbrain (optic tectum). This is the center for the optic 

 reflexes of accommodation, etc. 



By teasing away the gray matter of the pulvinar, optic pro- 

 jection fibers can be followed from the pulvinar to the occipital 

 pole of the cerebral hemisphere. The pulvinar and lateral 

 geniculate body are the thalamic centers, which, through their 

 connections with the cerebral cortex, provide for conscious 

 visual responses. See Bailey ('16), Fig. 358, p. 534; Cunningham 

 ('15), pp. 619, 620; Herrick ('15), Chap. XIV; Howell ('15), 

 Chaps. XVII-XIX inclusive, pp. 306-384; Morris ('14), Figs. 



