264 PRACTICAL HISTOLOGY [XXXIII 



3. Section through the exit of the 4<th nerve (man). 

 The ventral fibres of the sup. cer. peduncles decussate 

 in the middle line; the lateral fillet forms an oval 

 bundle on the dorso-lateral angle of the section; the 

 median fillet is much elongated and its lateral part 

 has a dorsal curve ; the cells of the locus coeruleus are 

 scattered and comparatively few. Note : 



The bundle of the 4th nerve issuing on each side 

 from the dorso-lateral angle of the grey substance, 

 and crossing over the aqueduct in the velum. 



4. Section through the exit of 4th nerve and anterior part of 

 pom (dog). The 4th nerve bundles arise laterally of the mid-brain 

 5th root ; on the dorso-lateral angle of the section is a piece of the 

 p. c. q. ; ventrally of this the large lateral fillet with grey substance 

 of the lateral fillet ; the sup. cer. peduncle consists of bundles of 

 oblique fibres, it is in this region much less conspicuous than in 

 man. The pes will probably be seen as an oval bundle immediately 

 ventral to the median fillet, and nearly free from pons fibres. 



5. Section through the posterior corpora quadri- 

 gemina (man). The pons fibres are now comparatively 

 few and probably are only present with some grey 

 substance in the middle region. On the lateral surface 

 of the central grey substance are the large round cells 

 of the mid-brain root of the 5th n. and the slender 

 half-moon shaped group of the large fibres forming the 

 root. (These will be seen in all sections up to the 

 anterior part of the a. c. q.) 



Note : the large mass of fibres of the pes or 

 crusta fairly distinct on the ventral surface on either 

 side. 



Dorsally of the crusta and stretching nearly up to 



