88 . THE BONES. 



great naturalist remarked that the area of the cranium diminishes as the animals 

 are further removed from the human type, while the area of the face increases 

 in the same sense. Colin has studied the heads of the domesticated animals 

 from this point of view. Putting to one side the surface occupied by the 

 einuses, he found that the area of the cranium to the face was as — 



1 : 2-69 in the Horse. 

 1 : 2 09 in the Ass. 

 1 : 3-43 in the Ox. 

 1 : 2-20 in the Ram. 

 1 : 1-95 in the Goat. 



3 24 in the Pig. 

 117 in the Dog. 

 0-68 in the Cat. 

 1-47 in the Rabbit. 

 054 in the Lamb. 



From this table it will be seen that, if the domesticated animals are classified 

 according to the area of the cranium, they will stand in the following order : 

 Cat, Dog, Rabbit, Goat, Ass, Ram, Horse, Pig, and Ox. 



4. Camper measured the facial angle by drawing two lines, starting from the 

 entrance to the nasal cavities, and passing towards the middle of the external 

 auditory canal and towards the most prominent part of the forehead. The facial 

 angle gives an idea as to the relative volume of the face and cranium, and the 

 dimensions of the latter ; but with animals it furnishes very imperfect information, 

 because of the form of the face and the development of the sinuses around the 

 cranial cavity. 



Colin has measured the facial angle of the domestic animals, by drawing two 

 lines from the upper incisors towards the external auditory canal and the fore- 

 head, in the point corresponding to the lower end of the brain ; and he obtained 

 the following average values : from 12° to 15° for the Horse ; 16° for the Ass ; 

 20° for the Bull ; from 20° to 25° for the Ram ; from 34° to 41° for Dogs ; and 

 41° for the Cat. 



On the other hand, we have measured this angle in Equines, and find that it 

 varies : in the Horse, between 11° and 13" ; in the Ass, between 12° and 16° ; 

 and in the Mule, between 13° and 15°. In the Hinny, it measures 14°. It is 

 somewhat remarkable that, in the Equid«, the Ass should have a greater facial 

 angle than the Horse. 



4. Modifications due to Age. 



Age brings modifications bearing upon the form of some regions of the head, 

 the development of external peculiarities of the bones, the shape of the cranium, 

 and its relations with the surface. 



1. It has been remarked that the development of the occipital tuberosity, 

 the temporal crests, and the lachrymal tubercle, increases with age in the Equine 

 species ; the infra-orbital foramen, which is frequently only a notch in youth, 

 becomes a true foramen when the animal is advanced in age. In the Foal, the 

 forehead is convex ; that bone and the nasal bones become flat as the creature 

 grows, and sometimes even the line of the nasal bones is concave in old age. The 

 maxillary region, which is at first convex, becomes gradually hollow as the molar 

 teeth are pushed out of the alveoli ; while the straight part of the posterior 

 border of the inferior maxilla becomes thin and sharp in very old Horses. The 

 entrance to the orbit is also notably modified, though its shape is not identical 

 in all the animals. In every instance, it has been remarked that the direction of 

 the larger axis of the orbital cavity, comprised at first in the plaue which passes 

 by the auditory canal and the implantation of the upper incisors, is depressed in 



