HISSING AND PROGRESSION. 21 



When alarmed, snakes .hiss with the object of frightening off 

 their enemies. If snakes were not able to make their presence 

 known, they would be frequently trodden upon and injured by 

 the various creatures of veld, forest, and mountain. For long 

 ages the wild animals have, from bitter experience, learned 

 to avoid snakes. The instinct has been so strongly developed 

 that it is transmitted from parent to offspring. This instinct 

 persists in a greater or lesser degree, even in domesticated 

 animals whose ancestors, perhaps for scores of generations, have 

 never seen a snake. Thus an animal will often manifest the 

 \vildest alarm at sight of a snake, or on hearing a snake hiss, 

 although it has never before come in contact with one of these 

 reptiles. This power of transmitting experiences is a wonderful 

 provision of Nature, for if every living creature had to learn 

 entirely by personal experience to avoid its enemies, and find out 

 what kinds of foods were wholesome, or the reverse, a great 

 number of species would rapidly become extinct. 



Venomous snakes invariably give a warning hiss, if suddenly 

 and unexpectedly approached or trodden upon. If the latter 

 should occur, they instantly bite the offender. 



Nature has therefore evolved the power of hissing as a means 

 of protection to the snake, and as a warning to other creatures 

 that a reptile capable of inflicting serious mischief upon them is 

 in dangerous proximity. 



Snakes progress or crawl about by means of their ribs and 

 belly scales. They also propel themselves by making forward 

 wriggling movements. This method is employed when they 

 move rapidly. The tail aids considerably in propelling the 

 body. The iDackbone of a snake is wonderfully constructed, and 

 is capable of being twisted and curved in a great variety of ways 

 without fear of dislocation. There are a great many vertebrae 

 to the backbone, often nearly three hundred. To each of 

 these sections a pair of ribs is attached, one on each side. The 

 heads of the ribs are loosely attached to the backbone sections, 

 and they can thus be moved forwards and backwards with the 

 greatest of ease. The extremities of the ribs are attached to the 

 scales or horny shield-plates of the abdomen. When the snake 

 crawls, the ribs along one side of its body move forward, the edges 

 of the scales gripping the rough surfaces of the ground, tree, or 

 object the snake may be crawling over. Then the ribs on the 



