52 ORAL EQUIPMENTS. 



growing to make good the surface wear, but arc only what arc 

 called " semi-persistent." We will refer to this again when 

 dealing with the teeth of Rodents. 



I have spent some time on this matter, because the com- 

 plexity of pattern of the molar teeth is used as a means of 

 classifying species and genera, and is of very great importance 

 to odontologists. 



Before leaving the horse let me refer to the " diastema " 

 where the bit goes. The great convenience of this inter- 

 space has led ignorant people to jump to the conclusion that 

 the horse was specially designed for the use of man ; but un- 

 fortunately for this theory the Hipparion, which is the horses' 

 remote ancestor and existed ages before man, possessed the 

 same interspace. 



The next great class are the Carnivora or flesh feeders, 

 though many of them also eat vegetable food: like some 

 bears, and vice versa many herbivorous quadrupeds eat flesh, 

 like the pig ; and according as the creature's habits of feeding 

 depart from the purely carnivorous diet, so do the teeth and 

 jaws depart from the typical carnivorous structure. 



As a general statement we may say that the characters 

 that distinguish a purely flesh diet are : the small size of the 

 incisors as compared with the canines, and their arrangement 

 in a straight line across the jaws ; the large size, deep im- 

 plantation, and wide separation from one another of the 

 canines, the reduction in number of the molar series, those 

 that remain being without broad crushing surfaces, in place of 

 Avhich a sharp pointed form prevails. 



If you will please look at our diagram of the skull of a 

 purely carnivorous creature, the tiger, it being taken as the type 

 form, you will find a very arched and shortened head ; huge 

 zygomatic arches (very small in herbivorous creatures) for 

 the attachment of the powerful " masseter " muscles ; very 

 deep glenoid cavities and condyles, lengthened in a lateral 

 direction, and teeth marked by being of a highly " sectorial " 

 or cutting character, and much reduced in number from 

 the typical mammalian dentition of 44. There is no play 

 allowed by the deep glenoid cavity for mastication either 

 forwards or backwards or from side to side, only an adaptation 

 for the cutting and prehensile conditions observed in the teeth. 

 Observe the strong pointed cruel canine tooth, so terribly 

 adapted to the prehension of living prey, the deep zygomatic 

 arch protecting the eyes from injury by branches of trees when 

 the creature is making its fatal spring, and suitable for attach- 

 ment of powerful muscles ; and the molar teeth — what could 



