668 MR FRANK J. COLE ON THE 



lies ventral to the other products of the division of vagus 1, and can only be seen when 

 these have been removed. Like the accessory pharyngeals of the glosso-pharyngeal, 

 this nerve is associated with the prse-branchial. It dips down suddenly and passes 

 straight forwards, first under the first branchial and then the hyoid arches. After coursing 

 forwards and slightly upwards for some little distance, it reaches and ends in the dorsal 

 internal surface of the pharynx, the external surface of the same part of the pharynx 

 being innervated by the accessory visceral branches of the IXth. 



Vagus 2. 



The second component of the vagus arises from the medulla immediately behind the 

 first. On leaving the vagus foramen it almost immediately expands into a ganglion, 

 which overlaps the ganglion on vagus 3, and passes outwards and slightly backwards. 

 Just distal to the ganglion the slender dorsal branch is given off (X 2 1 ), which soon 

 bifurcates and is distributed to the skin of the occipital region. Soon after, the motor 

 branch (X 2 7 ) is given off, and then the nerve passes over the first pharyngo-branchial 

 and lies in a furrow on the second similar to that previously described on the first. 

 The following branches are then given off : — 



(1) Pras-branchial (X 2 2 ). — Distributed to fifth demi-branch. It courses at the base 

 of the demi-branch, at some little distance from the arch, as far as the base of the latter. 

 There were no conspicuous branches, and the nerve was not found to be continued on to 

 the pharynx. 



(2) Post-branchial (X 2 3 ). — Su}3plies the sixth demi-branch. It runs somewhat 

 close to the arch at the base of the gill, and having reached the foot of the arch it takes 

 an inward turn and courses along the anterior edge of the arch, and thus reaches the 

 pharynx. There it divides into two, and runs obliquely forwards and inwards, but was 

 not traced far on to the pharynx. 



(3) Accessory skeletal branch (a) (X 2 4 ). — This arises from the prse-branchial, and 

 is doubtless a skeletal branch, though its distribution is not exactly typical. It is an 

 exceedingly fine nerve, and is associated with the posterior edge of the second branchial 

 arch. I did not, however, succeed in tracing it very far. 



(4) Accessory skeletal branch (b) (X 2 5 ). — Closely applied to the anterior edge of the 

 third branchial arch. This nerve has no obvious branches, and was not traced to the 

 base of the arch. 



(5) Accessory skeletal branch (c) (X 2 6 ). — Courses along the posterior edge of the 

 third branchial arch, and is a much finer nerve than X 2 5 . There were no conspicuous 

 branches, and I did not succeed in tracing the nerve right round the arch. 



(6) Motor branch (X 2 7 ). — Arises from the trunk of vagus 2 as described above, 

 and supplies a longitudinal band-like muscle lying over the gill arches a little to one side 

 of the mid-dorsal line. It is an exceedingly fine nerve, and may easily be overlooked. 



(7) Visceral proper (X 2 8 ). — This nerve, like its fellow of vagus 1 (X l 13 ), arises from 



