312 



UNGULATA 



A parallel modification has also taken place in the molar teeth of 

 the Proboscidea. 



As the hypsodont tooth is essentially a modification of, and, as 

 it were, an improvement upon, the brachydont, it is but natural to 

 expect that all intermediate forms may be met with. Even among 

 the Deer themselves, as pointed out by Lartet, the most ancient 

 have very short molars, and the depressions on the grinding surface 

 are so shallow that the bottom is always visible ; while in the Cervidce 

 of the more recent Tertiary periods, and especially the Pleistocene 

 and living species, these same cavities are so deep that whatever be 

 the state of the dentition the bottom cannot be seen. Some 

 existing Deer, as the Axis, are far more hypsodont than the majority 

 of the family ; and, on the other hand, many of the Antelopes (as 

 Tragelaplms) retain much of the brachydont character, which is, 

 however, completely lost in the more modern and highly specialised 

 Sheep and Oxen. 



Fig. 124.— Stomach of Ruminant opened to show internal structure, a, Oesophagus ; b, 

 rumen or paunch ; c, reticulum or honey-comb bag ; d, psalterium or manyplies ; e, abomasum 

 or reed ; /, duodenum. 



The complicated stomach of the Pecora (Fig. 124), which is 

 necessary for the performance of the peculiar function known as 

 "chewing the cud" — a function common also to the Tragulina 

 and Tylopoda — is divided into four well-defined compartments, 

 known as (1) the Rumen or Paunch, (2) the Reticulum or Honey- 

 comb Bag, (3) the Psalterium or Manyplies, (4) the Abomasum 

 or Reed. The paunch is a very capacious receptacle, shaped like a 

 blunted cone bent partly upon itself. Into its broader base opens 

 the oesophagus or gullet at a spot not far removed from its Avide 

 orifice of communication with the second stomach or honey- 

 comb bag. Its inner walls are nearly uniformly covered with a 

 pale mucous membrane, which is beset with innumerable close-set, 

 short, and slender villi, resembling very much the "pile" on 

 velvet The honey-comb bag is very much smaller than the paunch. 



