A TURTLE 159 



and passes to the muscles of the tongue and pharynx. The tenth 

 and eleventh nerves, the vagus, or pneumo gastric, and the spinal 

 accessory, arise each by a number of roots from the side of the 

 medulla; the former passes along the side of the neck to the 

 pharynx, larynx, lungs, and stomach ; the latter goes to the muscles 

 of the neck and shoulder. The twelfth nerve, the hypoglossal, 

 arises from the ventral surface of the medulla near its hinder end 

 and passes to the muscles of the tongue and throat. 



Exercise 36. Draw the lateral aspect of the brain on a scale of 3 or 4, 

 and show the origins and course of the cranial nerves so far as 

 observed. 



Remove enough of the skull to let the brain be taken out. 

 Place it in a dish of alcohol or water and study its ventral surface. 

 Identify the hemispheres and the olfactory lobes. On the ventral 

 surface of the diencephalon are the optic chiasma and the infundib- 

 ulum, the latter bearing at its distal end the hypophysis. The 

 ventral portion of the midbrain is formed by the crura cerebri. 

 Behind this is the medulla oblongata. 



Exercise 37. Draw the ventral aspect of the brain on a scale of 3 or 4. 



