THE XERVOUS SYSTEM 1491 



Ventral ochlear Tract. — The relays, or fresh supplies, of nerve- 

 fibres for this tract are furnished by the cells of the ventral nucleus. 

 The axons of these cells give rise to the trapezium, or corpus trape- 

 zoides, which is reinforced by the axons of the cells of the nucleus 

 trapezoides, and fibres from the superior olive of the same side. 

 The trapezoidal fibres cross the median plane, and thereafter con- 

 stitute the lateral or acoustic fillet, being further reinforced by fibres 

 from the superior olive of the side to which they have crossed, and 

 from the nucleus of the lateral fillet. The fibres of this fillet termi- 

 nate in the lower quadrigeminal body and internal geniculate body, 

 both of the same side. 



Dorsal Cochlear Tract. — ^The relays of fibres for this tract are 

 furnished by the cells of the lateral nucleus. The axons of its cells 

 form the striae acusticae, which cross the dorsal aspect of the resti- 

 form body and the floor of the fourth ventricle. At the median 

 line they pass forwards, and then cross to the opposite side. There- 

 after they join the lateral or acoustic fillet of the side to which they 

 have crossed. 



The lateral or acoustic fillet, as previously stated, derives its 

 fibres from the following sources : (i) The corpus trapezoides ; (2) the 

 striae acusticae; (3) the superior olive of both sides; and (4) the 

 nucleus of the lateral fillet. It serves as a path of connection 

 between the ventral and lateraV cochlear nuclei of one side, and the 

 lower quadrigeminal body and internal geniculate body of the 

 opposite side. 



It is to be noted that the ventral and lateral cochlear nuclei are 

 slightly connected with the lower quadrigeminal body of the same 

 side, but not with the corresponding internal geniculate body. 



The axons of the cells of the internal geniciilate body form a 

 corticifetal tract which passes to the cortex of the first or superior 

 temporal gyrus of the temporal lobe of the brain. 



The complex nervous chain associated with the cochlear nerve 

 may be tabulated as follows : 



1. The bipolar eells of the spiral ganglion. 



2. The fibres of the cochlear nerve. 



3. The ventral and lateral cochlear nuclei. 



4. The fibres of the corpus trapezoides, reinforced as stated. 



5. The striae acusticae. 



6. The internal geniculate body. 



7. The corticipetal tract from the internal geniculate body to the 



superior temporal gyrus. 



The cell-stations connected with this nervous chain are as follows: 



1 . The ventral cochlear nucleus. 5. The nucleus of the lateral 



2. The lateral cochlear nucleus. fillet. 



3. The nucleus trapezoides. 6. The lower quadrigeminal 



4. The superior olive of each body. 



side. 7. The internal geniculate body. 



Some of the fibres of the chain terminate in these cell-stations, 

 and others are derived from the axons of the cells which compose 

 the stations. 



