264 
Spirochaetosis 
advanced our knowledge of the mechanism whereby the tick infects the 
fowl. Without wearying you with the details of each experimenter’s 
work, I may summarize it as follows : 
The ticks are best rendered infective if they are maintained at 
a temperature of 30-35'’ C. after they have fed upon blood containing 
the spirochaete. If kept at a low temperature, 15-18° C., the spirochaetes 
disappear very soon from the ticks alimentary tracts, and they may bite 
birds repeatedly without infecting them. They may, however, be 
rendered infective after three months if placed at 80-35° C.: the 
spirochaetes then reappear in their coelomic cavity, as may be shown 
by cutting off one of the tick’s legs and examining the coelomic fluid 
which exudes from it upon a slide. 
When the spirochaetes first enter the tick they soon disappear from 
the gut, a certain number degenerate, whilst others traverse the 
gut wall and enter the coelomic cavity to circulate all over the body. 
A number of them die in this situation as evidenced by the frequent 
presence in the coelomic fluid of pale, scarcely visible, non-motile 
spirochaetes which are difficult to stain. The spirochaetes next enter 
the various organs, especially the cells of the malpighian tubules and 
sexual organs, in which they break up into a large number of small 
particles or coccoid bodies which multiply by fission and give rise to 
large agglomerations which can be seen very distinctly in stained 
specimens (Heidenhain stain). The coccoid bodies may also be found 
within the lumen of the gut and malpighian tubules and in the excreta. 
In the act of feeding, the tick occasionally voids excrement and exudes 
a few drops of secretion from coxal glands situated in the first inter- 
coxal space, the fluid pouring out of a wide duct and being rapidly 
secreted from the freshly imbibed blood serum. This fluid, as well as 
the salivary and intestinal secretion of Argas, contains an anti-coagulin, 
as I showed with Strickland. The coxal fluid dilutes the escaped 
excrement and facilitates its getting into the wound inflicted by the 
tick. This is doubtless the usual mode of infection, the coccoid bodies 
in the excrement gaining access to the blood of the host and afterwards 
developing into spirochaetes, though the latter development has not 
actually been followed. Marchoux and Couvy (1912) state that infection 
may, however, take place without coxal secretion being voided. The 
bird begins to show symptoms after a period of incubation of about four 
days following upon the bite of the infected tick. 
Although it was denied that the spirochaete of the fowl is transmitted 
hereditarily to the offspring of A. persious, I expressed the opinion 
