160 ON ANIMAL AND 



day ; and the common viper, we know, is an- 

 nually on the decline. \Ve must, therefore, 

 look for some other cause, independently of 

 climate, for this fortunate change in the natural 

 history of Europe; arid we shall probably find it 

 in the advance of cultivation and agriculture 

 peculiar to modern Europe, and to this country 

 in particular, by which impenetrable forests and 

 woods, that afforded shelter to, arid nurtured 

 such animals, have been cut down and cleared ; 

 extensive swamps, in which they were also to be 

 found, have been drained ; and the haunts of 

 venomous reptiles have, in every direction, been 

 disturbed or destroyed by the hands of the 

 cultivator. 



Though venomous serpents differ from each 

 other in magnitude, and in some of their external 

 characters; yet they all possess in common, cer- 

 tain leading features by which they may be 

 distinguished from the other classes which are 

 not poisonous. 



In the venomous, the head is flattened, scaly, 

 and large in proportion to the body ; the snout 

 is rather broad ; the neck is thick ; the skin is 

 of a dirty hue, and less variegated in its colour; 

 and the body does not taper towards the tail in 

 so fine a point. But the leading feature of dis- 

 crimination is in the formation of the upper jaw; 

 the venomous serpent having two, or more fangs 

 attached to it, projecting out on each side beyond 



