INSECTS AS INOCULATING NEEDLES 7 



water, and it is by means of the stabs of the adult 

 mosquitoes that malaria is spread from man to man. 

 The minute parasite that invades the blood of man 

 undergoes part of its development in the stomach of 

 the mosquito, whence it works its way into the 

 mouth glands, known as salivary glands. When the 

 insect pierces the human skin in order to suck blood, 

 the piercing organ, known as the proboscis, is moist 

 with the saliva from the mouth. In the saliva are 

 the active parasites. The proboscis acts like a 

 surgeon's needle, and the parasites of malaria are 

 passed or inoculated by it into the man. This mode 

 of infection is known as the inoculative method. 



Malaria is not the only malady transmitted by the 

 bite of insects. Just as the mosquito is the inter- 

 mediary between man and man in connexion with 

 the malarial parasites, so are the somewhat large 

 flies known as " tsetse" to the natives of West Africa, 

 the Congo, Uganda, and South Africa, in relation to 

 human sleeping sickness and cattle tsetse or fly 

 disease. The stabbing proboscis is laden with germs 

 of disease from the saliva, and by its action the latter 

 are transferred direct to their victim. 



Again, the inoculative method of infection is found 

 in the case of the various tick fevers or relapsing 

 fevers of Africa and Europe. The agents here are 

 not flies, however, but ticks. Redwater is a fatal 

 disease of cattle in the United States, and East 

 Coast fever causes great mortality in cattle in British 

 East Africa. The herds become infected by the 

 agency of different ticks which inoculate them with 

 the organisms responsible for the respective diseases, 



