l6o NERVE COMPONENTS OF BONY FISHES. 



Mammalia, and since in the two latter cases there are no 

 peripheral anastomoses between the rami of the VII and 

 V nerves, he is obliged to postulate ' ' an intra-cranial 

 fusion of the two nerves," the very existence of such an 

 anastomosis being a pure assumption. 



In Menidia, at any rate, it is clear that the exact reverse 

 is true, the apparent innervation from the facial in 

 reality being derived from the motor nucleus of the tri- 

 geminus, as there is no possible opportunity for a con- 

 fusion at any point between motor fibres of the V and 

 VII nerves. 



V. — The chorda tympani. — It may be regarded as estab- 

 lished that the chorda tympani in man supplies taste buds 

 on the anterior part of the tongue and glands and also per- 

 haps general mucous surfaces at the base of the tongue and 

 between it and the lower jaw. Its nerve fibres arise from 

 the geniculate ganglion of the facial and enter the brain 

 through the portio intermedia of Wrisberg, and internally 

 they are said to pass to the IX nucleus by way of the fas- 

 ciculus solitarius. Now, the fasciculus solitarius we homol- 

 ogize with the fasciculus communis of the Ichthyopsida and 

 hence it appears that the chorda both centrally and periph- 

 erally is a visceral branch of the facialis. That this nerve 

 is a pre-trematic branch is indicated by the peculiar 

 course of the chorda, through the tympanic cavity and 

 above and in front of the Eustachean tube, the latter being 

 regarded as the homologue of the spiracle. 



These homologies cannot be regarded as definitely 

 established; nevertheless they are greatly strengthened 

 by the direct embryological evidence brought out by 

 Dixon's work, On the Development of the Branches of the 

 Fifth Cranial Nerve in Man ('96). This author found 

 that the chorda tympani and large superficial petrosal 



