CRANIAL NERVES 



183 



in telodendra which interlace with dendrites from (mitral) cells in the olfactory 

 lobe, the interlacings forming oval bodies (glomeruli) in the lobe. The position 

 of the glomeruli varies (fig. 191). In elasmobranchs, some teleosts, ganoids, 

 snakes, some lizards, and mammals, the nerve is very short (fig. 191, A), while 



Fig. 191. — Diagrams of the dififerent kinds of olfactory bulb, tract, and nerve, ho, 

 olfactory bulb; g, glomeruli; ol, olfactory lobe; on, olfactory nerve; to, olfactory tract. 



the lobe is drawn out and differentiated into a distal enlargement, the olfactory 

 bulb containing the glomeruli, and a slender olfactory tract, the bulb being closely 

 applied to the olfactory surface. In some teleosts, amphibia, some lizards and 



Fig. 193. — Brain and olfactory and {nt) terminalis nerves of Scoliodon after Locy. 



turtles (fig. 191, B) the nerve is long and the olfactory lobe is not differentiated 

 into regions. In the gymnophiones the olfactory nerve has two roots, though 

 these are not to be compared with the dorsal and ventral roots of a spinal nerve. 



