36 



LABORATORY OUTLINE OF NEUROLOGY 



27. Now remove the brain from the cranial cavity, first care- 

 fully cutting the nerve-roots so as to permit their subsequent 

 identification and avoiding injury to the olfactory bulbs in front 

 and the pituitary body on the ventral surface. Examine the 

 ventral surface and complete the study of the parts listed in 

 Section 26. 



28. Make a transverse section across the medulla oblongata 

 at the level of the roots of the VIII nerves. Compare this sec- 

 tion with a similar one made in the vagus region (Fig. 6) and 

 note the differences. 



fourth ventricle 

 branchial 



pharyngeal nerve 



pre-branchial 

 nerve 



somatic sensory 

 column 



visceral sensory 

 column 



visceral motor 

 column 



somatic motor 

 column 



branchial nerve 



Fig. 6. — Diagrammatic cross-section through the medulla oblongata of 

 the dogfish in the region of the vagus nerve to illustrate the innervation 

 of the gills and the arrangement of the functional columns of the oblongata. 

 The groove between the visceral motor column and the visceral sensory 

 column is the sulcus hmitans. 



Draw the transverse section at the level of the VIII nerves and 

 designate on it the structures in the walls of the fourth ventricle 

 enumerated in section 23. 



29. Now divide the entire brain into two lateral halves by a 

 vertical median cut and study the course of the ventricles as 

 thus exposed, noting the narrowing of the fourth ventricle into 

 the aqueduct of Sylvius in the isthmus, its lateral expansion in 

 the optic lobes (optocele), the vertical expansion in the thalamus 

 (third ventricle), and the connection of the latter with the first 

 and second ventricles in the cerebral hemispheres through the 

 foramen of Monro {foramen interventriculare) on each side. 



