160 MR. ¥. J. COLE ON THE STKUCTURE AND MOKPJIOLOGY OF 



Beyond this the outer bviccal takes a sharp turn downwards, but before doing so crosses 

 internally the vertical portion of the infra-orbital canal almost at right angles, and takes 

 up a position in front of and above it. Shortly after giving off the twig to the 10th 

 sense organ, and as the outer buccal enters the posterior portion of the orbit, another twig 

 is given off, which, passing downwards and forwards, perforates the fifth sub-orbital and 

 siipplies sense organ 9 of the line. In front of this the outer buccal is seen to sej)arate into 

 three nerves. One of these is the main portion of Allis's nerve " c " (described above), 

 which, having hitherto accompanied the outer buccal, now passes upwards to its distri- 

 bution, whilst of the two ventral twigs the outermost passes outwards and downwards, 

 jjerforates the fourth sub-orbital, and innervates sense organ 8 of the infra-orbital canal. 

 The i-emaining one, in front of the twng to sense organ 8, takes a ventral curve, and 

 after giving off a branch ventrally which was traced to a pit organ situated ventral to the 

 canal, pierced tlie third sub-orl)ital and supplied sense organ 7 of the line. 



Tpnei^ hnccal branch. — This, the larger of the two divisions of the buccal trvmk, passes 

 downiwards and forwards, as previously described, across tlie orbit, and consists of two 

 l^arts. The lowei- and larger part soon gives off a twig which, after a long course down- 

 Avards and forwards (lying internal to the sclerotic), perforates the second sub-orbital and 

 supj)lies sense organ 6 of the infra-orbital canal. Almost opposite this sense organ 

 another twig is separated off from the lower ramus of the inner buccal, and in this region 

 the first and second sub-orbitals are seen in the sections to begin to overlajj. The twig 

 above pursues a course somewhat parallel to its predecessor, obliquely perforates the 

 lachrvnial, and supplies sense organ 5 of the line. At about the region of this sense 

 orean the two rami of the inner buccal begin to separate, tlie ventral one passing down- 

 Avards and approaching the infra orbital canal, whilst the dorsal ramus passes upwards. 

 Tlie ventral ramus opposite sense organ 5 gives off another twig, and, joassing rai^idly 

 downwards, lies near the inner face of the lachrymal, slightly dorsal to the upper border 

 of the infra-orbital canal. The twig above perforates the lachrymal at the doi'sal border 

 of the canal, and innervates sense oi-gan 4. After supplying this sense organ the 

 ventral ramus comes to lie immediately internal to the inner face of the lachrymal, and 

 exactly opposite the infra-orbital canal. It then gives off a branch which suj)plies 

 the pit organs ventral to the canal, and immediately afterwards the whole of the nerve 

 perforates the lachrymal and lies between that bone and the upper and lower borders of 

 the canal. Tliere are thus three perforations in the lachrymal for twigs of the ventral 

 ramus of the inner buccal to sense organs of tJie infra-orbital line. Before reaching the 

 third sense organ the ventral ramus divides into two — the ventral twig sujiplies sense 

 organ 3, whilst the dorsal passes forwards and supplies sense organ 2 only. 



To return to the upjier ramus of the inner buccal. After separating from the ventral 

 ramus it passes upwards and ventral to the nasal sack, and is joined by a branch of the 

 superior maxillary division of the trigeminus. The two nerves do not, however, mix. 

 The ujiper ramus then gives off its first branches, which terminate in the numerous pit 

 organs in the region of the snout between the supra- and infra-orbital lines. It now 

 passes downwards and becomes opposed to the inner face of the lachrymal at a spot 

 immediately dorsal to the place where the ventral ramus passes through its most 



