73 



i66. Olives. Transection of the oblongata 



through the olives. Weigert's hematoxylin method. Sections 



(A.. Now in alcohol. Clear and mount in alkaline balsam. 



Identify in this section the tracts already recognized : (a) the 

 pyramids, {b) the lemniscus, {c) the direct cerebellar tract, (rf) 

 ascending root of the Vth, and (e) the nucleus of the Xllth, (/) the 

 cuneate nucleus (and tract). Has the gracile nucleus disappeared ? 

 Note the (dentate) olivary nuclei causing the prominences upon 

 the lateral aspects of the oblongata (the olives). Are the fibers of 

 the Xth or Xllth nerves shown ? Note the extent of the cavity 

 (metacoele) ; the membranous roof (metatela) has been removed. 



167. Pons. Transection of the oblongata 

 through the pons. Weigert's hematoxylin method ; sections 



fjL. Now in alcohol. Clear and mount in alkaline balsam. 



Identify in the section (a) the pyramidal tracts, (5) the lem- 

 niscus, (c) the ascending root of the Vth, (d ) the posterior longi- 

 tudinal fasciculus. Does the section pass through the nuclei of the 

 Vlth, Vllth or Vlllth nerves ? Are any of these nerves shown ? 

 What has become of the restiform body? Note well the fibers 

 forming the mass of the pons, their decussation, relation to the 

 medipeduncle of the cerebellum ; the nuclei of the pons. 



MESENCEPHAI,. 



Gross preparations. In the region cephalad of the cerebel- 

 lum and pons, — the mesencephal, identify upon the dorsal aspect the 

 pregemina and postgemina (corpora quadrigemina, anterior and pos- 

 terior); upon the ventral aspect, the crura (cerebri) and the Hid 

 cranial nerve. 



168. Crura and Gemina (Pre- or Post-). . Tran- 

 section through the mesencephal. Weigert's hematoxylin method ; 

 sections )x ; now in alcohol. Clear and mount in alkaline 



balsam. 



In this section identify (a) the pyramidal tracts (the crusta), 



(^) the fillet, (f) the posterior longitudinal fasciculus. Note also 

 the central cavity (mesocoele) with the lining endyma, the central 

 cinerea surrounding it, the nucleus of the Hid nerve. I^ocate the 

 following parts: (/) the crusta, (2) the substantia nigra, (j) the 

 tegmentum, {4) the prepeduncles of the cerebellum, or their decus- 

 sation. Does the section include the red nucleus ? Is the Hid 

 nerve shown ? 



