Papillce and Nerves of the Tongue of the Frog. 281 



The nerves are derived from two pairs, the first of which 

 traverse a foramen together with the vagus at the base of the 

 cranium, between the occipital and sphenoid bones. The 

 second arise from the first cervical nerves, and traverse the 

 foramen between the first and second vertebra? of the neck. 

 Both pairs make a curve which is directed forwards and 

 downwards, and descend nearly in a parallel direction to the 

 hyoid bone, from whence they ascend to the concavity of 

 the lower maxillary and enter the tongue, where their main 

 trunks, much diminished in size, may be traced to the two 

 tubercles at its exlremitj^ The cervical nerves, which at their 

 commencement are nearly on the median line, and are internal 

 to the cranial pair at their origin, retain the same relative 

 jjosition until they enter the tongue, where they begin to ra- 

 mify, the two cranial nerves then becoming external. The 

 cranial nerve in its passage to the inferior maxillary bone tra- 

 verses the posterior belly of the digastricus, descends until it 

 reaches the hyoid bone, when passing under the middle and 

 over its great cornua, situate either beneath or by the side of 

 thehypoglossus muscle, continues in that position until it enters 

 the tongue, without giving oft' any branches to the muscles of 

 the neck. The cervical nerve follows nearly the same direc- 

 tion until it reaches the hyoid bone under which it passes, 

 and likewise places itself under the hypoglossus muscle, pene- 

 trating with the latter into the tongue, accompanied closely by 

 the lingual arteries and veins. It supplies numerous branches 

 to the muscles of the throat and neck. This nerve is much 

 more considerable than the former, and is much more curved. 

 The fifth pair or trifacial sends branches to the mucous mem- 

 brane of the mouth, which appear to reach the posterior part 

 of the tongue, but it gives oft' no nerves to that organ, corre- 

 sponding to the lingual branch of the inferior maxillary. 



Notwithstanding the transparency of the tongue when in a 

 state of distension, we find considerable difficulty in tracing 

 the ramification of its nervous trunks within the parenchyma. 

 At the upper surface, where they are most superficial, we may 

 under favourable circumstances, with tlie simple microscope, 

 be enabled to follow the various ramifications of a large branch 

 to a considerable extent, but we are unable either to command 

 ' a general view of the distribution of a single trunk, or of 

 distinguishing with any degree of certainty the ramifications 

 of one pair from another. 



The best mode to examine the nerves in the dead animal is 

 to disarticulate the lower jaw-bone on one side, and to divide 

 the throat on that side sufficiently to allow the jaw to be turned 

 completely backwards. The passage of these nerves may be 



