THE BULB. 

 FIG. 132. 



593 



ar.C.i 



Py.doc. 



--J fret. 



XII 



Py.dec. 



a.l.n. 



XII 



ol.a 



fa.i.' 



Transverse Dorso-ventral Sections of the Bulb (Man) at Different Levels. (Sherrington.) Fig. 

 132 and Figs. 133-137 form a series of transverse dorso-ventral sections of the brain taken at dif- 

 ferent levels from the hind end of the bulb to the front of the third ventricle; the several levels 

 are shown by the lines drawn in Fig. 131. They are all magnified twice. The details are shown, 

 for the sake of simplicity, in diagrammatic fashion ; the white matter is left unshaded, the course 

 of the fibres being indicated in a few important instances only; the gray matter is shaded for- 

 mally, the nerve-cells being indicated in the case only of the nuclei of the cranial nerves. The 

 want of complete bilateral symmetry which is often met with in such sections is indicated in 

 several of the figures. 



1. At the hind limit of the decussation of the pyramids ; 2. In the middle of the decussation; 

 3. At the upper end of the decussation ; 4. Just below the point of the calamus scriptorius ; 5. Just 

 above the point; 6. Through the middle of the ala cinerea. 



Py. Pyramids ; Py. dec. decussation of the pyramids ; Supra Py. dec. superior decussation ; /. a. i, 

 internal arcuate fibres ; /. a. e. external arcuate fibres ; Cb. position of cerebellar tract ; R. resti- 

 38 



