6 INTRODUCTORY CHAPTER. 
GENERAL CHARACTERISTICS. 
In every variety the dog is more or less endowed with a keen 
sight, strong powers of smell, sagacity almost amounting to 
reason, and considerable speed, so that he is admirably adapted for 
all purposes connected with the pursuit of game. He is also 
furnished with strong teeth, and courage enough to use them in 
defence of his master, and with muscular power sufficient to enable 
him to draw moderate weights, as we see in Kamtschatka and 
Newfoundland. Hence, among the old writers, dogs were divided 
into Pugnaces, Sagaces, and Celeres ; but this arrangement is now 
superseded, various other systems having been adopted in modern 
times, though none perhaps much more satisfactory. Belonging 
to the division Vertebrata, class Mammalia, order Fere, family 
Felide, and sub-family Canina, the species is known as Canis 
familiaris, the sub-family being distinguished by having two 
tubercular teeth behind the canines on the upper jaw, with non- 
retractile claws, while the dog itself differs from the fox with 
which he is grouped in having a round pupil in the eye instead 
of a perpendicular slit, as is seen in that animal. 
The attempt made by Linnzus to distinguish the dog as having 
a tail curved to the left is evidently without any reliable founda- 
tion, as, though there are far more with the tail on that side than 
on the right, yet many exceptions are to be met with, and among 
the pugs almost all the bitches wear their tails curled to the left. 
The definition, therefore, of Canis familiaris caudd (sinistrorsum) 
recurvatd, will not serve to separate the species from the others of 
the genus Canis, as proposed by the Swedish naturalist. 
HABITAT. 
In almost every climate the dog is to be met with, from Kam- 
tschatka to Cape Horn, the chief exception being some of the 
islands in the Pacific Ocean; but it is only in the temperate zone 
that he is to be found in perfection, the courage of the bulldog 
and the speed of the greyhound soon degenerating in tropical 
countries. In China and the Society Islands dogs are eaten, 
