280 COMPARATIVE ANATOMY AND PATHOLOGY. 
of the bloodhound. I select these dogs from certain points of re- 
semblance between them — the one can hunt only by the eye, the 
other, perhaps, sees not his victim until he pounces upon it. We 
readily account for this, from the natural formation of the different 
animals. In the contracted cranium of the greyhound, there is not 
room for the proper development of the olfactory nerve — nor for 
that of the ethmoid bone in the upper portion of the nasal cavity. 
In the cranium of the bull-dog and of the pug there is scarcely 
room for any development of the ethmoid bone, and there is no 
species of dog in which the sense of smell is so deficient. 
The Swine . — In him the development of olfactory power occu- 
pies a middle rank between that of the herbivorous and carnivorous 
animal. His teeth mark him as an omnivorous quadruped, and 
the organs of smell correspond with this indication. In his natural 
state he lives altogether on vegetable food, and it is only when 
he becomes domesticated that the nature of his aliment is changed. 
The ethmoid and the turbinated bones in the hog occupy an inter- 
mediate grade between those of the horse and the dog. There is 
a diminution of the cell-like structure. It is more laminated and 
spiral and complicated than in the horse, and a more extensive 
surface is offered for the expansion of the olfactory nerves ; there- 
fore, although naturally herbivorous, he is prepared to be rendered 
omnivorous by domestication, and there are painful stories on re- 
cord of his becoming most fearfully carnivorous. 
As roots form a great part of the natural food of the hog, he is 
furnished with a strong muscular snout, callous at the extremity 
for turning up the soil, and a large plexus of nerves takes its course 
down each side of the nose, and is ramified on the snout. A sense 
of a peculiar kind is probably resident here, by which the animal 
is enabled to distinguish with greater accuracy the nature and 
properties of substances hidden under ground*. 
The Seal . — This is another carnivorous animal, of the occa- 
sional, although rare domestication of which there are some pleas- 
ing histories on record, and a useful and attached servant he proved 
himself to be. Sir B. Harwood gives an interesting account of 
the olfactory apparatus in him. “ A bone of very intricate 
structure occupies nearly the -whole of each nostril. When viewed 
in front, it resembles a section of the arbor vitae of the cerebellum. 
The principal trunk is attached to the rising arch of the maxillary 
bone, and directs its course downwards, until it approaches within 
one-third of its length, to the os palati. Eight or more principal 
branches arise from this trunk ; and each of them is afterwards 
divided and sub-divided until the eye is weary in following them. 
Harwood, p. 41. 
