A NATURALIST IN BRAZIL 



seizes its head, and presses its cheeks together (Plate 30), so that 

 the venom trickles from the fangs into a bowl held beneath it. 

 This virus is injected into horses, in gradually increasing doses, 

 until they become immune, when a serum is prepared from their 

 blood. There are special sera — for example, rattlesnake serum — and 

 a mixed serum with which any snake-bite may be treated. One 

 carries a phial of this serum on one's travels, and a small hypodermic 

 syringe. If one is bitten by a venomous snake one injects a little 

 serum into the skin round the wound, or between the wound and 

 the heart, and one may then be sure that no serious results will 

 ensue. The Butantan Institute is therefore a national blessing. 



Much more unpleasant than the venomous snakes, and beyond 

 comparison more dangerous, are the bloodsucking insects of Brazil. 

 If I am asked what dangerous creatures there are in India and 

 Brazil I do not speak of the tigers, leopards, jaguars and snakes, 

 but only of the mosquitoes. These are the enemies which one really 

 has reason to fear in the tropics, for they are the carriers of malaria, 

 and the still more dangerous yellow fever. 



But here again the reader must not be too greatly alarmed. One 

 thinks of mosquitoes as particularly formidable insects. As a matter 

 of fact there are plenty of mosquitoes in Europe. The species that 

 carries malaria may be found in Baden. When the disease itself is 

 not prevalent the mosquitoes cannot convey it, and are therefore 

 harmless. But when during the war malaria was introduced into 

 certain war prisoners' camps from South Russia, malaria made its 

 appearance here and there among the people of Baden, as I saw 

 with my own eyes. 



The conveyance of malaria is effected as follows : In the blood of 

 a malarial patient live millions of tiny living creatures. These make 

 their way into the red corpuscles of the blood, multiply therein, 

 and wander off into other corpuscles, while the corpuscles thus 

 attacked are decomposed, so that each time the parasites multiply 

 the patient has an attack of fever. If the malarial mosquito bites 

 a person suffering from malaria, it sucks in the parasites together 

 with his blood, and these become encysted in the wall of the insect's 

 intestine, and presently their offspring find their way to the salivary 

 glands of the insect. With the saliva of the mosquito, which the 

 insect injects into the wound in order to prevent the blood from 

 coagulating, the malarial parasites enter the blood of a healthy 

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