6 INTRODUCTORY CHAPTEE. 



effects of habit on structure, it is not perhaps straining the point 

 to attribute the forward direction of the eyes in the dog to the 

 constant habit, for many successive generations, of looking for- 

 ward to his master, and obeying his voice." w 



Such is the state of the argument in favour of the original 

 descent from the wolf, but, as far as it is founded upon the breed- 

 ing together of the wolf and dog, it applies also to the fox, which 

 is now ascertained occasionally to be impregnated by the dog ; 

 but in neither Gase we believe does the progeny continue to be 

 fertile if put to one of the same cross, and as this is now ascer- 

 tained to be the only reliable test, the existence of the first cross 

 stands for nothing. Indeed, experience shows us more and more 

 clearly every year, that no reliance can be placed upon the test 

 depending upon fertile intercommunion, which, especially in birds, ' 

 is shown to be liable to various exceptions. Still it has been 

 supported by respectable authorities, and for this reason we have 

 given insertion to the above extract. 



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 is now superseded, various other systems having been adopted in 

 Bell's British Quadrupeds, pp. 196, 197. 



