NEUROLOGY 





decussate across the midline to the opposite colliculus. Other fibers from the 

 superior brachium pass into the stratum opticum (upper gray-white layer). Some 

 of these turn upward into the gray cap while others terminate among the cells 

 of this layer. Since the superior colliculi appear to be the central organs con- 

 cerned in the control of eye-muscle movements and eye-muscle reflexes we should 

 expect to find them receiving fibers from other sensory paths. Many fibers pass to 

 the superior colliculus from the medial fillet as the latter passes through the teg- 

 mentum bringing the superior colliculus into relation with the sensory fibers of the 

 spinal cord. Fibers from the central sensory path of the trigeminal probably pass 

 with these. Part of the ventral spinocerebellar tract (Gowers) is said to pass up 

 through the reticular formation of the pons and mid-brain toward the superior 

 colliculus and the thalamus. The superior colliculus is intimately connected with 

 the central auditory path (the lateral lemniscus), as part of its fibers pass the 

 inferior colliculus and terminate in the superior colliculus. They are probably 

 concerned with reflex movements of the eyes depending on auditory stimuli. The 

 superior colliculus is said to receive fibers from the stria medullaris thalamis of 

 the opposite side which pass through the commissura habenulse and turn back 

 to the roof of the mid-brain, especially to the superior colliculus. By this path 

 both the primary and cortical olfactory centers are brought into relation with the 

 eye-muscle reflex apparatus. 



The fibers which pass to the nuclei of the eye muscles arise from large cells in 

 the stratum opticum and stratum lemnisci and pass around the ventral aspect 

 of the central gray matter where most of them cross the midline in the fountain 

 decussation of Meynert, and then turn downward to form the ventral longitudinal 

 bundle. This bundle runs down partly through the red nucleus, in the formatio 

 reticularis, ventral to the posterior longitudinal bundle of the mid-brain, pons and 

 medulla oblongata into the ventral funiculus of the spinal cord where it is known 

 as the tectospinal fasciculus. Some of the fibers are said to pass down with the 

 rubrospinal tract in the lateral funiculus. Some fibers do not decussate but pass 

 down in the ventral longitudinal bundle of the same side on which they arise unless 

 possibly they come from the opposite colliculus over the aqueduct. From the 

 ventral longitudinal bundle collaterals are given off to the nuclei of the eye muscles, 

 the oculomotor, the trochlear and the abducens. Many collaterals pass to the red 

 nucleus, and are probably concerned with the reflexes of the rubrospinal tract. 

 The fibers of the tectospinal tract end by collaterals and terminals either directly 

 or indirectly among the motor cells in the anterior column of the spinal cord. 



The superior colliculus receives fibers from the visual sensory area of the occipital 

 cortex; they pass in the optic radiation. Probably no fibers pass from the superior 

 colliculus to the visual sensory cortex. 



The Olfactory Nerves (/ cranial) or nerves of smell arise from spindle-shaped 

 bipolar cells in the surface epithelium of the olfactory region of the nasal cavity. 

 The non-medullated axons pass upward in groups through numerous foramina in 

 the cribriform plate to the olfactory bulb ; here several fibers, each ending in a tuft 

 of terminal filaments, come into relation with the brush-like end of a single den- 

 drite from a mitral cell. This interlacing gives rise to the olfactory glomeruli of the 

 bulb. The termination of several or many olfactory fibers in a single glomerulus 

 where they form synapses with the dendrites of one or two mitral cells provides for 

 the summation of stimuli in the mitral cells and accounts in part at least for the 

 detection by the olfactory organs of very dilute solutions. Lateral arborizations 

 of the dendrites of the mitral cells and the connection of neighboring glomeruli by 

 the axons of small cells of the glomeruli and the return of impulses of the mitral 

 cells by collaterals either directly or through the interpolation of granule cells to the 

 dendrites of the mitral cells reinforce the discharge of the mitral cells along their 

 axons. The axons turn abruptly backward in the deep fiber layer of the bulb to 



