334 A MANUAL OF DENTAL ANATOMY. 



This is a fair illustration of the fact that although in 

 nature it is generally the same tooth which is modified to 

 perform the function of a canine, it is not invariably the 

 same ; for here in the same animal are two different teeth 

 in the upper and lower jaw thus respectively modified. 



And as they are different teeth, it happens that the upper 

 canine closes in front of the lower. 



There is reason to believe that there was some difference 

 in the size of canines between the male and female oreodon. 



The hollow-horned ruminants (sheep and oxen and ante- 

 lopes), and likewise almost all the solid horned ruminant 

 (deer) have the following dental formula : 



.00 3 3 

 1 3 C Ti P 3- m 3- 



The lower incisors are antagonised not by teeth, but by 

 a dense gum which clothes the fore part of the upper jaw ; 

 if a sheep is watched as it feeds, it will be seen to grasp the 

 blades of grass between the lower teeth and the gum, and 

 then to tear them off by an abrupt movement of the head, 

 as it would be impossible for it to, strictly speaking, bite 

 it off. 



The anomaly of the entire absence of upper incisors was 

 held to have been diminished by the statement of Goodsir, 

 who believed that uncalcified tooth germs were to be found 

 in the foetuses of many species. As this was precisely what 

 might have been expected, it has since that time passed 

 current as an established fact ; but recently M. Pietkewickz, 

 working in the laboratory of M. Ch. Robin, has absolutely 

 denied the occurrence of even the earliest rudiments of 

 tooth germs in this situation, after an examination of a 

 series of foetuses of the sheep and cow, ranging even from 

 the earliest periods. (Journal d' Anatomic, par C. H. Robin, 

 1873, p. 452.) Since meeting with this statement I have 

 had no opportunity of verifying this matter myself. 



