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Show 1895.1 SENSOEY CANAL SYSTEM OF FISHES. 281 The whole of the sensory canal system of the head is innervated by the trigeminal, facial, and glossopharyngeal; the lateral canal is innervated by the lateralis division of the vagus. The trigeminal group may be divided into the following main branches, viz.:- 1. The ramus ophthalmicus superficialis. 2. The ramus ophthalmicus profundus. 3. The ramus buccalis. 4. The ramus maxillaris. 5. The ramus mandibularis. 6. The ramus oticus. 7. The ramus lateralis. Of these seven rami all but the rami ophthalmicus profundus, maxillaris, and lateralis innervate some portion of the sensory canals. 1. The ramus ophthalmicus superficialis is with the ramus lateralis, the most dorsal branch of the group. It passes off from the Gasserian ganglion immediately above the ramus ophthalmicus profundus, but not, as mentioned by Ramsay Wright (13. p. 366), through a large foramen. It traverses tbe dorsal border of the orbit, and then along the upper surface of the skull, supplying a series of cluster-pores in the region of the nasal capsule, and also the sense-organs of the supra-orbital branch. 2. The ramus ophthalmicus profundus lies immediately below the ramus ophthalmicus superficialis; after passing through the orbit it branches and enters into connection with the ram as ciliaris. 3. The ramus buccalis arises lateral to the ramus ophthalmicus profundus and beneath the ramus ophthalmicus superficialis. It passes forwards and divides into two branches; the lateral branch passes along the borders of the sub-orbital branch of the main sensory canal, to which it gives off a number of fine branches ; the inner branch of the buccalis does not innervate any portion of the sensory canal system. 4 & 5. The ramus maxillo-mandibularis.-I cannot agree with ProfessorRamsayWright's diagram of these nerves1 (13. pi. iv. fig. 1). In the final specimen I dissected, which measured 287 millim. in length, I found the ramus maxillaris considerably larger than the ramus mandibularis ; the buccalis lies just above it (PI. XVIII. fig. 2). A few small branches pass off to the integument, the main branch passing to the maxillary region and innervating the maxillary barblet, on which it divides in four branches, passing between the divided tendon of the retractor muscle. The ramus mandibularis.-In its upper region it is connected with the ramus maxillaris, dividing into external and internal branches on the anterior edge of the mandibular adductor muscle; the former-the ramus externus-passes along the lower jaw, innervating the mandibular portion of the operculo- 1 Professor Eamsay Wright informs m e that part of the work was done on A. niger, which may possibly account for sqme of the differences, |