CHAP. IX ] 



THE SKULL OF THE DOG. 



n7 



other. For this purpose a young animal, still retaining the 

 milk teeth, will be best. 1 



The skull has a longitudinal central axis (the cranio-facial 

 axis, Huxley), around which all its parts are arranged, and 



an 



FIG. 46. Longitudinal and vertical section of the skull of a Dog (Canisfauiiliaris). 

 with mandible and hyoid arch, A. an anterior narial aperture; M T raaxillo- 

 turbinal bone; ET ethmo-turbinal ; Na nasal; ME ossified portion of the 

 mesethmoid ; CE cribriform plate of the ethmo-turbinal ; Fr frontal ; Pa parietal ; 

 IP interparietal ; SO supraoccipital ; F.xO exoccipital ; BO basioccipital : Per 

 periotic ; BS basisphenoid ; Pt pterygoid ; AS alisphenoid ; OS orbitosphenoid ; 

 PS presphenoid ; PI palatine ; / 'o vomer ; MX maxilla ; PMx premaxilla ; 

 sh stylohyal ; ek epihyal ; ch ceratohyal ; bh basihyal ; th thyrohyal ; 5 symphysis 

 of mandible ; cp coronoid process ; cdfcondyle ; a angle ; id inferior dental canal ; 

 the mandible is displaced downwards to show its entire form ; the * indicates the 

 part of the cranium to which the condyle is articulated. 



its structure will be best understood by commencing with 

 the description of the bones forming this axis. 



1 When the zoologist wishes to throw into the strongest relief the 

 distinctive characters of different species, he selects for comparison fully 

 adult examples ; when the anatomist wishes to trace their community of 

 structure and their resemblances, younger specimens are better adapted 

 for his purpose. 



