248 APPENDIX. 



"We never experienced the slightest injury from them ourselves, 

 personally, although we lived two months in their ' habitat,' which was 

 in this case as sharply denned as in many others, for the south bank of the 

 Chobe was infested by them, and the northern bank, where our cattle were 

 placed, only fifty yards distant, contained not a single specimen. This was 

 the more remarkable, as we often saw natives carrying over raw meat to 

 the opposite bank, with many tsetse settled upon it. 



" The poison does not seem to be injected by a sting, or by ova placed 

 beneath the skin, for, when one is allowed to feed freely on the hand, it is 

 seen to insert the middfe prong of three portions, into which the proboscis 

 divides, somewhat deeply into the true skin : it then draws it out a little 

 way, and it assumes a crimson colour as the mandibles come into brisk 

 operation. The previously shrunken belly swells out ; and, if left undis- 

 turbed, the fly quietly departs when it is full. A slight aching irritation 

 follows, but not more than the bite of a mosquito In the ox this same 

 bite produces no more immediate effects than in man, it does not startle 

 him as the ' gadfly' does ; but a few days afterwards the following 

 symptoms supervene : the eye and nose begin to run, the coat stares as if 

 the animal were cold ; a swelling appears under the jaw, and sometimes at 

 the navel ; and, though the animal continues to graze, emaciation com- 

 mences, accompanied by flaccidity of the muscles, and this proceeds 

 unchecked until, perhaps months afterwards, purging comes on, and the 

 animal, no longer able to graze, perishes in a state of extreme exhaustion. 

 Those which are in good condition often perish soon after the bite is 

 inflicted ; with blindness and staggering, as if the brain were affected by 

 it. Sudden changes of temperature produced by falls of rain seem to 

 hasten the progress of the complaint, but in general the emaciation goes 

 on uninterruptedly for months, and, do what we will, the poor animals 

 perish miserably. 



" When opened, the cellular tissue on the surface of the body beneath 

 the skin is seen to be injected with air, as if a quantity of soap bub- 

 bles were scattered over it, or a dishonest awkward butcher had been 

 trying to make it look fat. The fat is of a greenish-yellow colour, and of 

 an oily consistence. All the muscles are flabby, and the heart often so 

 soft that the fingers may be made to meet through it. The lungs and 

 liver partake of the disease. The stomach and bowels are pale and empty, 

 and the galUbladder is distended with bile. 



" These symptoms seem to indicate, what is probably the case, a poison 

 in the blood, the germ of which enters when the proboscis is inserted to 

 draw blood. 



" The poison-germ, contained in a bulb at the root of the proboscis, 

 seems capable, although very minute in quantity, of reproducing itself, for 

 the blood after death by tsetse is very small in quantity, and scarcely stains 

 the hands in dissection. 



" I shall have, by and by, to mention another insect, which by the same 

 operation produces in the human subject both vomiting and purging. 



" The mule, ass, and goat enjoy the same immunity from the tsetse 

 as man and the game. Many large tribes on the Zambesi can keep no 

 domestic animals except the goat, in consequence of the scourge existing 

 in their country. 



" Our children were frequently bitten, yet suffered no harm ; and we saw 



