c i. \7 />./■: 



545 



A caecum is always present, sometimes short and simple, but when 

 long it is folded upon itself in a characteristic manner. 



The characters of the base of the cranium are shown in Fig. 8 



Fig. 240.— Right lateral aspect of the skull of the Dog (Canis familiarU). 



(p. 38), where it will be seen that the auditory bulla is inflated, 

 although it has only a ruclimental internal septum ; the paroccipital 

 process, although in contact with the bulla, is 

 prominent, and there is a large glenoid foramen. 

 In all the existing forms the humerus has lost the 

 entepicondylar foramen ; the crowns of the upper 

 molars are triangular in shape (Fig. 251), and the 

 blade of the upper carnassial consists of two lobes. 



In the alimentary canal the caecum (Fig. 250) is 

 extremely characteristic. It is a simple appendage 

 of nearly uniform width (about equal to that of the 

 ileum) attached to the side of the canal, just beyond 

 the ileo-csecal valve, and with a rounded termination. 

 In a Dog of average size it is 5 or 6 inches long if 

 uncoiled, but it is normally folded by its mesenteric 

 attachments backwards and forwards several times 

 on itself by the side of the ileum, after the manner 



shown in the figure. 



The existing Dogs form a very compact group, 

 with numerous species closely resembling each other 

 in essential characters, though differing considerably 

 externally. The most marked differences are slight p I0 . 250.— 

 variations in the number of the true molar teeth, Cecum of the Arc- 

 which exceed the usual number in the Cape Long- ™\ " iieum^r 

 eared Fox (Otocyon), and fall short of it in some other colon, in the nat- 

 less aberrant forms to which the names of Icticyon ural i" ,sition the 

 and Cyon have been given, and a diminution in the mos J t . 

 number of toes in the Cape Hunting Dog (Lycaon), 

 which has 4-4, instead of 5-4 as in the remainder of the family. 



35 



