SPIROCH^TES IN TICKS 79 



the opportunity of confirming Leishman's work. By 

 experiment it was proved that infected salivary fluid 

 was not the common means of inoculating the virus, 

 but that other body excretions of 0. moiibata were 

 concerned. Two other excretions of 0. moubata are 

 well known. The tick possesses important nitrog- 

 enous waste-excreting organs (Malpighian tubules), 

 which discharge their fluid into the gut. A clear 

 fluid from glands near the junction of the legs and 

 body the coxal glands is also excreted. Now, by 

 detailed experiments, it has been shown that the 

 Malpighian secretion is the main infective agent. 

 When a tick sucks blood, a clean-cut wound is made 

 by its jaws. Blood passes steadily into the body of 

 the tick, and presently the clear coxal fluid is ejected 

 from the body and forms a thin layer on the under- 

 surface of the tick. This fluid is non-infective. But 

 towards the end of the feeding the denser Malpighian 

 fluid is voided, becomes diluted by the coxal fluid, 

 and flowing over the under-surface of the body of 

 the tick, and into the wound made by the jaws, it 

 transmits the parasite to the new host. 



The changes undergone by the spirochsete in the 

 tick may now be described. When the organisms 

 are swallowed by the tick, they pass into the gut, 

 where some of them are digested, while others resist 

 digestion for a considerable time. They may remain 

 as spirochsetes in the alimentary canal for periods 

 which vary in their duration according to the 

 temperature at which the tick is kept. Some of the 

 spirochaetes pass through the wall of the gut and 

 reach the fluid in the body cavity, where they often 



