274 



THE NERVOUS SYSTEM 



tention to the more important facts. Cajal (1911) has carried out extensive 

 investigations concerning the structure and connections of the olfactory parts 

 of the brain both in man and the smaller macrosmatic mammals, especially the 

 mouse. His results, which differ in many respects from the ideas previously 

 current, have been brought together in his "Histologie du Systeme Nerveux," 

 Vol. II, pp. 646-823. The account which follows is largely based on his work. 



Fig. 206. Horizontal section of the rostral portion of the cerebral hemispheres of a mouse to 

 show the anterior commissure. Golgi method. A, anterior and B, posterior portions of anterior 

 commissure; G, anterior column of the fornix. (Cajal.) 



Structure and Connections of the Olfactory Bulb. In the olfactory portion 

 of the nasal mucous membrane there are located bipolar sensory cells, each with a 

 thick peripheral process, the ciliated extremity of which reaches the surface of 

 the epithelium. These are the olfactory neurons of the first order, and their 

 slender central processes are the unmyelinated axons which constitute the olfac- 

 tory nerves. These fibers are gathered into numerous small bundles, the fila- 



