THE NERVOUS SYSTEM. 105 



a. The white substance. How is it arranged ? 



b. The gray substance. How thick is it ? 



c. A gray mass, the corpus dentatum, is in the centre of 

 the white substance in each lateral lobe. 



d. Sketch. 



VI. THE MEDULLA OBLONGATA. 



Make a transverse section of the medulla and note the 

 arrangement of the gray matter within. Make another 

 through the pons, and note the arrangement of the fibres 

 which compose it. 



E. The Microscopical Structure of the Brain. 



Material. A prepared section of the cerebral cortex of the human 

 brain. 



Apparatus. A compound microscope. 



Examine a prepared section of the human brain. 



THE NERVE CELLS. 



Note : 



a. Their size, shape, and structure. 



b. Protoplasmic or branched processes are called dendrites. 



c. The unbranched process, or axon, is continued as the 

 axis cylinder of a nerve fibre. Each nerve cell with all 

 its processes, both dendrites and axons, is called a neuron. 

 Do all cells possess both kinds? 



d. Draw cells showing all these parts. 



e. How do nerve cells differ from epithelial and muscle 

 cells ? 



