Chap, xviii.] CEREBRUM AND CEREBELLUM. 149 



of the glossopharyngeal nerve ; and, lastly, but more 

 outwards and upwards, several divisions of the nucleus 

 of the auditory nerve. The nerve-fibres, originating 

 in these nuclei, pass in bundles through the substance 

 of the medulla oblongata, so as to appear on the 

 antero-lateral surface. Of course these nerves, the 

 nuclei of which are situated nearer to the middle line 

 e.g.., the hypoglossal and spinal accessory have to pass 

 through the reticular formation, whereas those whose 

 nuclei are situated more laterally pass only through 

 the lateral part of the medulla. 



CHAPTER XVIII. 



THE CEREBRUM AND CEREBELLUM. 



194. THE structure of the dura mater, arachnoidea, 

 and pia mater of the brain is similar to that of the 

 same membranes of the cord. 



As has been shown by Boehm, Key and Retzius, 

 and others, the deeper part of the dura contains peculiar 

 ampullated dilatations connected with the capillary 

 blood-vessels, and representing in fact the roots of the 

 veins. 



The glandulce, Pacchioni, or arachnoidal villi of 

 Luschka, are composed of a spongy connective tissue, 

 prolonged from the sub-arachnoidal tissue and covered 

 with the arachnoidal membrane. These prolongations 

 are pear-shaped or spindle-shaped, with a thin stalk. 

 They are pushed through holes of the inner part of 

 the dura mater into the venous sinuses of this latter, 

 but are covered with endothelium. Injection matter 

 passes from the sub-arachnoidal spaces through these 

 stalks into the villi. The. spaces of their spongy 



