470 
S^)irocliaeta ffciUinarum 
infection, but that it is produced by the excretion of infective material 
which enters the open wound caused by the tick’s bite. 
In support of this view I might mention that, although the majority 
of Argas persicus do not emit their coxal fluid and excrement whilst 
attached to the fowl, yet a few were noticed to pass their secretion 
immediately after feeding. In these cases the excreted substance 
bathed the open wound caused by the tick’s bite. The injection into 
a Java sparrow^ of some of this material—coxal fluid mixed with 
excrement—from one tick was followed by a severe spirochaetal infection, 
and yet, in practice, it is generally necessary to feed numerous ticks on 
a bird in order to produce an infection. I believe that the reason of 
this latter fact is that, as a rule, only those few Argas which emit their 
coxal fluid and excrement whilst on the bird are responsible for the 
infection. The fact that spirochaetes may be found in the salivary 
glands is evidence that these organs may be infective, but as both the 
spirochaetes and the resulting coccoid bodies often disappear from this 
part of the tick, it is evident that it is not a favourable situation for 
their development. 
Many of the spirochaetes remain in the lumen of the gut and it is 
in this situation that one observes the formation of the coccoid bodies 
with the greatest clearness. One to two days after the parasites have 
been ingested into the gut of the tick, by examination with dark-ground 
illumination, large numbers of spirochaetes may be observed undergoing 
this process of the formation of the coccoid bodies. As a result the 
spirochaetes rapidly disappear from the gut of Argas (in three to ten 
days, according to the temperature), whereas, when infected blood is 
merely kept in a sealed glass tube, the parasites may persist for as long 
as three mouths and show various stages of degeneration, some of 
which have been described above (Fig. 3). 
The resulting coccoid bodies persist in the lumen of the gut and 
Malpighian tubules and are excreted together with the Malpighian 
secretion. When the crystals escape from the Malpighian tubule tbe 
intracellular coccoid bodies may also become free and thus the Malpighian 
secretion is continually infected, and when mixed with the coxal fluid it 
may enter the open wound caused by the tick’s bite. The coccoid bodies 
would then be able to develop into spirochaetes in the blood of the bird, 
although this process has not actually been followed. 
The development of the intracellular coccoid forms into normal 
1 These birds are not more susceptible to S. gallinarum than fowls. From their 
small size they are more convenient for inoculation experiments. 
