120 THE ARTISTIC ANATOMY OF ANIMALS 



which corresponds to the first molar tooth, to terminate, 

 after a course more or less prolonged, at the alveolus 

 of the canine. This space, more or less considerably ex- 

 panded, which thus separates these teeth is called the inter- 

 dental space ; but this denomination is not applicable to 

 ruminants, because these latter possess neither canine nor 

 incisor teeth in the upper jaw (see p. 125, dentition of the 

 ox and sheep). The superior maxillary bone of one side and 

 that of the opposite side do not meet in the median line in the 

 region which corresponds to the incisor teeth ; they are sepa- 

 rated by a bone which, in the human species, is present only 

 at the commencement of life, and aftersvards coalesces with 

 the maxilla ; this is the intermaxillary or incisor bone. 

 This bone, which is paired, is formed of a central part, which 

 bears the superior incisor teeth ; it is prolonged upwards 

 and backwards by two processes : one, external, which in- 

 sinuates itself between the superior m^axillary and the nasal 

 bone, except in the sheep, in which it remains widely separ- 

 ated from the latter ; the other, internal, which is united to 

 that which belongs to the bone of the opposite side to form 

 part of the floor of the cavity of the nasal fossae ; the external 

 border of this process, which is separated from the body of the 

 bone by a notch, forms the internal boundary of the corre- 

 sponding incisor opening or the incisor slit. Owing to the 

 absence of superior incisors in ruminants, the intermaxillary 

 bone presents no alveoli. 



The malar bone, and the os unguis or lachrymal, are 

 more or less developed according to the species considered. 

 With regard to the malar bone, it is most important to 

 notice the part which it takes in the form^ation of the 

 zygomatic arch, and that its inferior border contri- 

 butes to form the crest to which is attached the masseter 

 muscle. 



As for the nasal bones, they present differential characters 

 which, as they affect the form of the region which they 

 occupy, are worthy of notice. 



Their dimensions in length are proportional to those of 

 the face. Very small in man, they are more developed 

 in carnivora. We recognise in the latter the two curves 



