chap. ix. J THE SKULL OF TL1E DOG. 97 



from each 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 



j-r F>a IP 



CE \ 



45. — Longitudinal and vertical section of the skull of a Dog {Cants familiaris , 

 with mandible and hyoid arch. £. an anterior narial aperture; MP maxillo- 

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

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

 IP interparietal: SO suprnoccipital ; ExO exoccipital ; BO basioccipital " Per 

 periotic ; BS basisphenoid ; Pt pteryg id ; AS alisphenoid ; OS orbitosphenoid ; 

 PS presphenoid ; PI palaiine ; Vo vomer ; Mx maxilla ; PMx premaxilla ; 

 s!i stylohval ; eh epihyal ; ch ceratohyal ; bk basihyal ; th thyrohval ; j symphysis 

 of mandible ; cp coronoid process ; cd condyle ; 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. 



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

 I its structure will be best understood by commencing with 

 i 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 

 tor his purpose. 



