100 PHYSIOLOGY FOR THE LABORATORY. 



each side into the middle peduncles of 

 the cerebellum. 



c. The mid-brain. 



1. The optic tracts are two bundles of fibres coming 



obliquely forward over the front part of the 

 peduncles and meeting in the centre to form 

 the optic chiasma. What is the meaning of 

 this crossing ? What relation does it bear to 

 the optic nerves and the sensation of light ? 



2. The tuber cinereum is the small triangular or 



nearly quadrilateral area at the anterior part 

 of the crura cerebri in the angle of diver- 

 gence of the optic tracts. 



3. The infundibulum extends from the tuber cinereum 



to the pituitary body that may have been 

 torn off in removing the brain from the skull. 

 Notice the cavity in the infundibulum. 



4. The pineal gland is the small body above the 



corpora quadrigemina. 



5. Sketch the details in your dorsal, ventral, and 



lateral views of the brain. 



B. The Motor and Sense Areas. 



The surface of the cerebrum has been partly mapped 

 out into motor and sense regions. These are divided into 

 areas for the muscle-groups belonging to different members 

 of the body; the foot, the arm, etc. The stimulation of 

 a certain part of an area for the arm results in movements 

 of extension, the stimulation of another part of the area 

 results in flexion of the arm. Moreover, each area may 



