73 



166. Olives. Transection of the oblongata 

 through the olives. Weigert's hematoxylin method. Sections 



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

 Identify in this section the tracts already recognized : O) the 

 pyramids, () the lemniscus, (<r) the direct cerebellar tract, (d) 

 ascending root of the Vth, and (<?) 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 



/t. Now in alcohol. Clear and mount in alkaline balsam. 



Identify in the section (a) the pyramidal tracts, () 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 t Are any of these nerves shown t 

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

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

 medipeduncle of the cerebellum ; the nuclei of the pons. 



MESKNCKPHAL. 



Gross preparations. In the region cephalad of the cerebel- 

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

 pregemina and postgernina (corpora quadrigemina, anterior and pos- 

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

 cranial nerve. 



1 68. Crura and Gemina (Pre- or Post-). . Tran- 

 section through the mesencephal. Weigert's hematoxylin method ; 

 sections // ; now in alcohol. Clear and mount in alkaline 



balsam. 



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



(3) the fillet, (<:) 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. Locate 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 ? 



