92 PROFESSOR J. C. EWART AND MR J. C. MITCHELL ON THE 



which later unites with an offshoot from the lateral canal. The third and fifth tubules 

 terminate in the hyomandibular canal ; but the fourth and sixth, which are nearly 1'50 

 cm. in length, simply communicate with the canal as they pass obliquely outwards. 



Passing to the ventral surface, the outer or straight part (suborbital and orbito-nasal 

 of Garman) opens to the exterior by nine extremely short tubules (t.-t. 22 , fig. 7) ; the 

 middle part (nasal of Garman) by seventeen tubules (t.-v. 33 , fig. 7), twelve short ones 

 external to the naso-buccal groove, and five, slightly longer, internal to the groove ; and 

 the inner (prenasal) part gives off, from about its middle third, eleven tubules (t.-t. m , 

 fig. 7). The direction of the tubules is indicated in the figure. 



Innervation. — The first part of the infra-orbital canal is supplied by a slender nerve 

 which springs from the buccal division of the facial as it separates from the superficial 

 ophthalmic part of the facial. This nerve (6m. 1 , fig. 6) runs upwards posterior to the 

 eyeball, and breaks up into six terminal branches, which enter the canal as represented 

 in figure 6. For the next segment of the canal, two slender nerves spring from the 

 buccal as it passes forwards under the eyeball. These nerves arch outwards, the first 

 enters the canal nearly opposite the first tubule, the second by three branches opposite 

 the origin of the three following tubules. To supply the middle portion of the canal on 

 the dorsal surface a somewhat larger nerve springs from the buccal as it appears from 

 under the eyeball. This nerve, as it turns outwards and forwards, breaks up into 

 eleven branches, eight of which enter the canal opposite the eight remaining tubules, 

 while three terminate in the canal immediatelv in front of the tubules. 



ml 



The buccal, having given off this branch, divides into an internal and an external 

 portion — the inner (bu. 1 , fig. 7) runs forwards above the palato-quadrate cartilage, and is 

 mainly concerned in supj)lying the inner buccal group of ampullae ; while the outer (bu. 2 , 

 fig. 7) runs obliquely outwards, and sends the most of its fibres to the outer buccal group 

 of ampullae. From this outer division of the buccal, a branch passes forwards and inwards 

 to supply the remainder of the dorsal part of the infra-orbital canal, the branch pene- 

 trating the canal by six slender filaments. Supplying the ventral part of the infra-orbital 

 canal, as far back as its junction with the supra-orbital (S.O. 5 , fig. 7), are nine twigs, 

 which spring from a second branch from the outer division of the buccal that usually, at 

 first, accompanies the one just described. The remainder of the outer part of the canal 

 (orbito-nasal) is supplied by six slender nerves which also spring from the outer division 

 of the buccal. The outer division of the buccal thus supplies the outer straight ventral 

 portion, and the anterior part of the dorsal portion of the infra- orbital, i.e., part of the 

 suborbital and the orbito-nasal of Garman ; the rest of the suborbital and the orbital of 

 Garman being supplied by branches which spring from the main trunk of the buccal as 

 it passes forwards under the eyeball. 



The remaining ventral portion of the infra-orbital canal is supplied by the inner 

 division of the buccal nerve. As the nerve reaches the anterior margin of the palato- 

 quadrate cartilage it sends branches both outwards and inwards, while the main portion 

 runs forwards to enter the inner buccal group of ampullae, from which a few fibres escape 



