MAMMALIA. 075 



Man,* there is a group, apparently a continuation of the molar, 

 which mounts up along the superior maxillary bone, beneath the 

 zygoma, even to behind the globe of the eye. The excretory ducts 

 derived from this group pierce the mucous membrane near the 

 posterior margin of the superior alveolar ridge; such an arrange- 

 ment is met with in the Ox, the Sheep, and the Horse. 



In the AMPHIBIOUS MAMMALIA the salivary system is very 

 feebly developed ; and in the GET ACE A, as might be expected 

 from their habits, no salivary glands whatever are to be detected. 



(754.) Before considering the mechanism of deglutition in the 

 Mammalia, we must, in the next place, briefly describe their hyoid 

 apparatus ; more especially as this remarkable system of bones, 

 which in the lower Vertebrata was so importantly connected with 

 the respiratory function, is now reduced to an extremely simple 

 condition, and, although it is still intimately connected with the 

 larynx, is more particularly remarkable, as forming a centre of 

 attachment for almost all the muscles of the throat. 



Perhaps there is no part of the bony framework of the body 

 that exemplifies more strongly than the os hyoides the impossi- 

 bility of attaining correct physiological views relative to the compo- 

 sition of the skeleton by the mere examination of the human sub- 

 ject. Let the student, for instance, compare for a moment the os 

 hyoides of Man with that of the Fish, or of the Amphibious Rep- 

 tile, and endeavour, in the simple segment of a circle presented by 

 the one, to find the analogues of the body and complicated arches 

 of the others; then, doubtless, he will find that, without some inter- 

 mediate gradations of form, it is not easy to trace the slightest rela- 

 tionship between them. 



The human os hyoides consists of a central portion and two cor- 

 nua; but these are generally so completely consolidated as to form 

 but one bone, which is connected by the interposition of a broad 

 ligament with the upper margin of the thyroid cartilage ; moreover, 

 two smaller appendages, called the lesser cornua, are articulated with 

 the upper surface of the hyoid bone, close to the point of junction 

 between the cornua majora and the body; from whence ligaments, 

 called the stylo-hyoid, pass upwards and backwards to the styloid 

 processes of the temporal bone. 



All the apparatus of hyoid arches passing between the body 

 of the bone and the base of the cranium, which were so largely 



* Le9ons d'Anat. Comp. torn. iii. p. 210. 



2x2 



