Other Diseases Transmitted by Insects 167 1 



made so far seem to indicate that they make their 

 way directly from the proboscis into the new host. 



Soon after entering the circulatory system of the 

 human host the parasites make their way into the 

 lymphatics where they attain sexual maturity, and 

 in due time new generations of the larval filariae 

 or microfilariae are poured into the lymph, and 

 finally into the definite blood-vessels, ready to be 

 sucked up by the next mosquito that feeds on the 

 patient. 



In most cases of infection the presence of these 

 filariae in the blood seems to cause no inconvenience 

 to the host. They are probably never injurious in 

 the larval stage, that is, in the stage in which they 

 are found in the peripheral circulation. 



In many cases, however, the presence of the 

 sexual forms in the lymphatics may cause serious 

 complications. The most common of these is that 

 hideous and loathsome disease known as elephan- 

 tiasis in which certain parts of the patient becomes 

 greatly swollen and distorted. An arm or a leg 

 may become swollen to several times its natural 

 size, or other parts of the body may be seriously 

 affected. 



In some of the South Sea Islands 30% to 40% of 

 the natives are afflicted in this way, some only 

 slightly others seriously. There is little or no pain, 



