RUMINANTIA. 



533 



gle example will illustrate the points most 

 deserving of attention. 



The true molar tooth of the permanent 

 series has a quadrilateral form, its outer and 

 inner lateral surfaces being bounded by mar- 

 gins more or less convoluted. The crown in 

 the young state presents four elevated cusps, 

 which, by subsequent attrition, disappear. 

 The ground surface, thus flattened, is marked 

 in the centre by double crescent-shaped 

 ridges of enamel, so disposed as to present, 

 along with the central mass of dentine and 

 external crust of cemctitum, alternate layers 

 of hardened tissue, having different degrees of 

 density. By such an arrangement it conse- 

 quently follows that the enamel being the 

 least affected by trituration, remains some- 

 what above the level of the other dental sub- 

 stances, a condition highly favourable for the 

 due performance of mastication, and one re- 

 sulting in all cases from the vertical folding 

 of the original formative capsule. The upper 

 molars of certain individuals present an ac- 

 cessory island-shaped portion of enamel at 

 the internal border, by which the extent of 

 grinding surface becomes enlarged. This 

 additional facet only makes its appearance in 

 a tooth which has been employed for some 

 time, as it depends upon the wearing down 

 of a columnar fold which is developed at the 

 side between the lobes, and which does not 

 extend so high up as the summit of the 

 crown in the unworn tooth ; it is well 

 seen in the Ox and Deer (p, fig. 356.) 



Fig. 356. 



Molar tooth of the Deer. 

 (From Owen's " Odontography.") 

 Tongue. The lingual organ undergoes 

 certain modifications, in accordance with the 

 habits and kind of aliment on which the ru- 

 minant subsists. These peculiarities do not 

 involve any material departure from the type 

 of structure invariably found'in other mam- 

 mifers ; on the contrary, the muscular ele- 

 ments and their relations to surrounding parts 

 remain nearly the same. The deviations of 

 which we have to speak principally refer 

 therefore, to the form of the organ and its 

 epidermal covering. In Ruminantia, more 

 than in almost any other order, the tongue is 

 specially designed to fulfil the offices of pre- 

 hension as well as deglutition, and it neces- 

 sarily follows that the several portions of the 

 machine destined to carry out such com- 

 plicated functions, exhibit a corresponding 

 complexity of development. Those regions, 

 arbitrarily denominated by the anthropotomist 



the root, body, and tip, acquire great signifi- 

 cance in this group of animals, being mor- 

 phologically indicated on the dorsal aspect 

 of the organ ; and they not only manifest a 

 structural distinctiveness, but the functions 

 over which they preside subserve different 

 purposes. The anterior moiety is employed 

 in collecting, and perhaps in some measure 

 ascertaining the nature of the food ; the 

 second aids in adjusting and preparing the 

 morsel, but is more particularly concerned in 

 thrusting the bolus backward into the oeso- 

 phageal cavity ; while the third circumscribes 

 and regulates the movements of the organ in 

 its entirety, acting from the point cTappui of 

 the hyoid bone (Zaglas). 



The surface of the tongue is armed with 

 forms of papillae similar to those of Man and 

 other mammalia. Two kinds, namely, the 

 simple^/j/brm and fungiform, are conspicuous 

 and very numerous on the dorsal aspect of 

 the elongated prehensile portion in front, and 

 two other varieties the conical and circum- 

 vullate occupy the dorsum towards the 

 root, leaving the inter-molar region com- 

 paratively free. Of those papillae at the 

 fore part, the simple filiform are curved back- 

 Fig. 357. 



Torgue of the Giraffe. (From Owen.) 

 M M 3 



