POISONED WOUNDS. 469 



which, independently of any local irritation, the whole system 

 becomes fatally affected. 



The tsetse is a harmless looking insect, very little larger than 

 a house fly ; its bite is innocuous to man, goat, antelope, pig, 

 ass, and all wild animals, and even to the calf whilst sucking ; 

 but fatal to the horse, domestic cattle, sheep, and dog. The 

 symptoms do not arise immediately after the infliction of the 

 bite, but after an interval sometimes of several weeks. There 

 is then an appearance of general disorder, with weakness and 

 emaciation ; running at the eyes and nose, and glandular swell- 

 ings under the jaws ; continual w^asting of the body, and finally 

 death. 



The districts infested by the tsetse are very distinctly de- 

 fined, although separated from a healthy one by a narrow river, 

 or even an inperceptible boundary, beyond which an animal is 

 never affected, unless it has been into a district infested by the 

 fly. It appears that nothing has been ascertained respecting 

 the nature of the plants or vegetation, or whether anything peculiar 

 grows in such districts; but travellers seem satisfied that the tsetse 

 fly is never found except where the elephant and rhinoceros 

 abound, and that in proportion as those animals are destroyed 

 do the ravages of the tsetse diminish. 



The Poison of Snakes and Vipers. — All the truly venomous 

 vertebrata belong to the order of ophidian reptiles, which is sub- 

 divided into two large groups or sub-orders, distinguished from 

 each other by clearly defined peculiarities of organization. In 

 one of these sub-orders, the viperina, the species of which it is 

 composed are all more or less venomous ; whilst in the others, 

 the colubrina, of which the harmless ringed snake of this 

 country is an example, the majority are innocuous as regards 

 their bite, but formidable otherwise : for example, the boa 

 constrictor. 



Characteristics of the venomous Viperina. — Body comparatively 

 thick and clumsy ; the general aspect sombre and lurid ; and the 

 usual movements sluggish and dull. The tail is thick, and very 

 short ; the head broad, depressed, and triangular, or cordiform, 

 joined to the trunk by a constricted neck, and covered on the 

 summit with small scales, not plates or scutes, and having the 

 skin usually loose and wrinkled ; the eyes are small, wholly 

 lateral, deeply lodged in the sides of the head, and shaded above 



