yo TSETSE FI,Y POISON. 



its perfect harmlessness in man and wild animals, and 

 even calves so long as they continue to suck the cows. 

 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 defined 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 middle 

 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 man- 

 dibles come into brisk operation. The previously 

 shrunken belly swells out, and, if left undisturbed, the 

 fly quietly departs when it is full. A slight itching irrita- 

 tion follows, but not more than in 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 gad- 

 fly does ; but a few days afterwards the following symp- 

 toms 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 commences, 

 accompanied with a peculiar flaccidity of the muscles, 

 and this proceeds unchecked until, perhaps months after- 

 wards, 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 staggering and blindness, 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 ot soap-bubbles 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 



