586 



THE NERVOUS SYSTEM 



the other cranial nerves. In reality it is a representative of the olfactory lobes 

 of other animals, which are part of the cerebrum. The olfactory lobe origi- 

 nates as an offshoot from the cerebral vesicle, the front part of which is de- 

 veloped into the bulb of the olfactory nerve, while the back part forms its 

 peduncle. The nerve, the cavity of which in man is filled up in the fully de- 

 veloped condition with neurogliar substance, lies upon the cribriform plate 

 of the ethmoid bone, and is contained in a groove on the under surface 



CORP. 



FIG. 416. Scheme of the Central Connections of the Optic Fibers. (Cunningham.) 



of the frontal lobe. On examination of the bulb it is found to be thus made 

 up: Beneath the neurogliar layer is a layer of longitudinal fibers and a few 

 nerve cells next ta this is a layer of small cells, nuclear layer, fibers from the 

 layer of nerve fibers passing through it. 



The nuclear layer is also separated into groups of cells by an interlacing 

 of the fibers. The next layer is thick and is composed of neuroglia and nerve 

 fibers, some of which are medullated, as well as of cells more or less pyra midal 

 in shape. Below this layer is the layer of olfactory glomeruli. These glomer- 

 uli are small synapses of olfactory fibers. The larger also includes small 



