Herrick, Cranial Nerves of Ambly stoma. 197 



enters the otic capsule by a foramen which is distinct from that 

 of the saccular ramus, after having received, as above stated, 

 about half of the fibres of the common dorsal root of the trige- 

 minus and the acustico-facialis. While still within this foramen 

 it divides into the two trunks above mentioned. The ramus 

 aciisticus utriculi seems to contain about half of the fibres which 

 enter the cephalic ramus from the ventral root. It passes al- 

 most directly laterad distributing a large number of fibres to 

 the macula utriculi by means of a very short but thick ramulus 

 aciisticus utriculi (r. a. u.) and sending two smaller branches, the 

 ramulus aciisticus externa {r. a. e.) and the ramulus aciisticus an- 

 terior (r. a. a.) to the external and anterior cristae respectively. 

 The ramulus ac. utriculi is not mentioned by Arnold as occur- 

 ring in Pipa, though it is described by Retzius in Rana 

 esculenta. 1 



It will be noticed that this sharp separation of the two 

 roots of the acustico-facialis at the ganglion, taken together with 

 the fact that one root is distributed exclusively to the sacculus 

 and the acustic fibres of the other exclusively to the utriculus, 

 accords well with the morphological theories of Ayers [2] re- 

 garding the composite nature of the eighth nerve and the des- 

 cent of its two rami from the ninth and seventh nerves respect- 

 ively. The connection of the utricular ramus with the seventh 

 is here sufficiently obvious. The ninth, however, originates 

 some distance behind the eighth, and neither enters the otic 

 capsule nor at any point comes into relations with the eighth 

 nerve. As Professor H. W. Norris is at present engaged upon 

 a study of the development of the ear of Amblystoma the first 

 part of which has already been published [4], I refrain from 

 any further comment on this interesting region. 



As stated above, the facialis leaves its ganglion in com- 

 pany with the ramus acusticus utriculi. Separating from the 

 latter, it leaves the otic capsule through several foramena, after 

 having previously received the large branch from the dorsal root 



Quoted by George Haslarn in his translation of Ecker's Anatomy of the 

 Frog, p. 396. 



