BREATHING AND HISSING OF SNAKES. 149 



We may almost compare this pulmonary action to the 

 panting or full breathings of ourselves under alarm or 

 agitation. Only, in comparison as the lung of snakes is 

 elongated, and there is so much of it to fill with air, so is 

 the sound prolonged, and the breathing a slower process. 



There is another viper, the small Cape adder {Vipera 

 atropos), a most deadly little reptile, in which a similar sound 

 to that of the ' puff adder ' may be heard. When this crea- 

 ture is disturbed, it draws in a long breath which expands 

 its whole body in the same manner, and then in expelling 

 the air, a long sort of wheeze or blowing is audible. Even 

 in drawing the breath in, a slight sound is heard (as it also 

 is in our native viper and some others) ; but instead of the 

 prolonged hiss by which most snakes display their agitation, 

 this little adder expresses itself in long successive blowings, 

 like its larger relative ariefans, only a little less regularly. 

 In the present instance, I saw the lung inflated with an 

 agitated undulating motion, as if the fluid air were entering 

 in little waves. I do not state positively that this is in- 

 variably the case from having witnessed it in one specimen. 

 This might be the normal process, or this viper's lungs and 

 health may have been impaired. I am thus precise because 

 it is unsafe to establish as an invariable fact in natural 

 history what may have been seen only occasionally, a habit 

 which has so often led to the promulgation of erroneous 

 impressions. 



The prolonged sound of the hiss in snakes is due to the 

 size of the lung, they having a large supply of air to draw 

 upon. Some serpents expand their bodies under excitement 

 without any perceptible hiss : the cobra both hisses and 



