286 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



trematic -f- pharyngeal branch, and a lower R. post- 

 trematicus. The former passes forwards, and divides into 

 two rami, both of which at once turn downwards and back- 

 wards. These are the R. pharyngeals (ph. x. 1) and the R. 

 pre-trematicus (pre. 1). The pharyngens courses down- 

 wards and immediately breaks up in the mucous mem- 

 brane of the roof of the mouth. The pre-trematicus 

 reaches the first branchial arch, lying just internal to the 

 undivided post-trematicus ix. When the latter divides it 

 thereafter accompanies the ventral division of it, but 

 curves round the inner aspect of the elbow formed by the 

 epi- and cerato-branchials. 



The R. post-trematicus (post. 1.) gives off below just 

 at its origin a motor branch, and shortly afterwards curves 

 downwards, outwards and backwards to reach the second 

 branchial arch. There it divides into two branches, just 

 as in the ixth, and these bend externally round the epi- 

 and cerato-branchial elbow, one lying above the cerato- 

 branchial and the other below it. Thereafter their course 

 resembles that of the post-trematicus ix. 



2. — T. branchialis secundus Vagi (t. x. 2). 



The ganglion of this division is more or less massed 

 with the remaining vagus ganglia (g. x. 2-5), and their 

 boundaries are difficult to determine. The truncus arises 

 from the internal surface of the ganglionic mass, like the 

 first. A small mixed plexus of communis and motor 

 fibres, not shown in the chart, may be described here. It 

 arises by 3 roots — one from the second branchial ganglion, 

 and two from the third. These three roots form a plexus 

 from which 3 nerves arise, two of which pass forwards and 

 inwards and break up in the roof of the pharynx, whilst 

 the third also passes forwards as a purely motor 

 nerve, 



