THE SKATE. 79 



206. The distal ends of the olfactory lobes (Fig. 22, olf\ 

 each forming a slightly convex white band on the dorsal 

 surface of the corresponding nasal sac. 



XLIV. Remove one of the nasal sacs, and note 



207. Its cup-like form, the cavity being open below. 



208. The ridges into which its lining of mucous mem- 

 brane is raised : they are arranged in two rows at right 

 angles to a central ridge. 



XLV. Remove the eye with its remaining muscles, and 

 set it aside for future examination. 1 Dissect out 



209. The second division of the fifth nerve (Figs. 22 and 27, 

 F 2 ), arising mainly from the posterior fasciculus mentioned 

 in 1 86, but also receiving fibres from the anterior fascicu- 

 lus : it passes forwards and slightly outwards, and divides 

 into two chief branches, an internal, the palato-nasal 

 nerve ( V 2 *) and an external, the maxillary nerve ( F 2b ) 

 the former passing directly forwards alongside the cranial 

 wall and beneath the eye muscles, and the latter passing 

 outwards- and forwards towards the antorbital cartilage 



( 35). 



210. The third division of the fifth, or mandibular 

 nerve (^ 3 ), arising mainly from the anterior, but receiving 

 fibres from the posterior fasciculus : it runs parallel with the 

 common trunk of the second division as far as the bifurcation 

 of the latter, and then takes a course internal to and nearly 

 parallel with the maxillary nerve. 



The three divisions of the fifth nerve supply between them all the 

 anterior part of the head : the orbito-nasal goes to the dorsal region of 

 the rostrum and nasal capsule, and to the gelatinous tissue in their 

 neighbourhood : the palato-nasal to the ventral region of the same parts, 

 as well as to the fronto-nasal process and the nostrils ; it also sends 



1 The eye must be dissected in the fresh condition : for directions see 

 LI I., p. 84. 



