XXXII] THE SPINAL BULB 261 



11. Section through the locus coeruleus. 



The general features are much as in the previous section, 

 except as regards the 5th nerve and its nuclei ; there may be 

 large bundles of 5th nerve near the surface, and small portions 

 of the motor and sensory nuclei. Note : 



In the grey substance at the lateral angle of the ventricle 

 about half-a-dozen large round cells the lower part of the 

 mid-brain nucleus of the 5th nerve, and just outside these a 

 bundle of large nerve fibres the mid-brain root of the nerve. 



Just beneath the grey substance of the floor of the ventricle 

 at its lateral angle a marked group of oval nerve cells the cells of 

 the locus cceruleus ; with a higher power most of them are seen 

 to be pigmented. 



Dog. In 10 the pyramids are in the midst of the pons fibres 

 and their nuclei; the bulbar root turns out rather abruptly, in a 

 section at this point the sensory nucleus is large, the motor small ; 

 the upper olive is probably present. 



In a section made a little more anteriorly, the motor nucleus is large 

 and the sensory small; olive and trapezium fibres are absent, the 

 comma-shaped sup. cer. ped. is obvious at the side of the ventricle. 



In 11 the cells of the locus cceruleus are unpigmented ; the sup. 

 cer. ped. is a little more ventral than in 10; the division of the fillet 

 into median and lateral can be seen. 



DEMONSTRATION. 



Series of sections of spinal bulb after section of the cord. 

 (Marchi's method.) Follow the dorsal cerebellar tract running 

 in the middle of the restiform body, and the ventral cerebellar 

 tract running with the superior cerebellar peduncle ; both ending 

 in the middle lobe of the cerebellum. 



