266 PRACTICAL HISTOLOGY [XXXIII 



8. Section through the commissure of the p. c. q. (dog). The 

 substantia nigra is in larger amount ; the medial fillet is more lateral 

 and its dorso-lateral part consists of oblique fibres separated by a 

 little grey substance (anterior mid-brain fillet). Note : 



The commissure of the p. c. q., consisting of numerous nerve 

 bundles above the aqueduct ; (the similar fibres in man are less 

 distinct since they are much scattered in grey substance). 



9. Section through the posterior part of the an- 

 terior corpus quadrigeminum and above the pons (man). 

 Note : Dorsally of the large pes, now free from pons 

 fibres, a deeply stained mass, the substantia nigra. 



In the tegmentum a large round mass, the decus- 

 sated sup. cer. ped. with some grey substance amongst 

 the bundles. 



The medial fillet divided into two portions, one 

 between the sb. n. and the lateral part of the sup. cer. 

 ped., the other more dorsal with oblique fibres directed 

 towards the a. c. q. (anterior mid-brain fillet). On the 

 surface just ventral to the a. c. q. an elongated oval 

 mass of fibres, the brachium of the p. c. q. 



The nucleus of the 3rd nerve, dorsally and a little 

 laterally of the p. 1. b. : fibres of the 3rd nerve run from 

 the nucleus, and others issue near or through the medial 

 part of the pes. 



The deep white layer of the a. c. q. consisting of 

 bundles of fibres forming a white line to the eye in the 

 ventral part of the a. c. q. 



10. Section through the posterior part of tlie 

 a. c. q. (dog). 



The interpeduncular ganglion is not present, the fillet is much 

 broken up into small bundles. 



