140 
Sinrocliaetosis 
exceedingly rapid circular movement was maintained, which gave the 
whole the appearance of a faintly visible ring. It was only when the 
rotation stopped for a second or so that the spirillar structure could be 
seen and the short appendix I have drawn be detected. On a few 
occasions I succeeded in seeing the organism sideways and then it 
appeared to me that it was not only rotating in a circle, but also 
around its own axis. The membrane I have already mentioned could 
then be made out as a very faint outline. It is an integral part of the 
spirochaete and I do not think that it can be considered to be a laked 
erythrocyte. 
Similar but smaller bodies have been described by Butler in 
S. didtoni when kept outside the body. Globose swellings have been 
seen by Carter in the spirochaetes occurring in Southern Arabia. 
Schellack (1908) also describes similar appearances in S. novyi after 
washing them in saline solution ; Karwacki observed the rolling up 
into a sj^iral of S. recurrentis in I’elapsing fever blood kept in a leech. 
Fantham’s (1911, p. 491) observations on these features, or at least 
somewhat similar ones, are of interest. 
“Encystruent of Spirochaetes has been described by several writer’s. Up to the 
^rresent, neither in the Spirochaetes of the blood nor in those of Lamellibranchs have 
I found true encystment. Two types of pseudo-cyst forms have, however, been 
encountered : 
1. The Spirochaete becomes more closely coiled, either about its centre or 
nearer one end, so that a ball-like form is produced. This ball simulates a cyst 
with the body of the Spirocha.ete protruding from either end....But this form is only 
temporary, the Spirochaete irncoiling after a short time and swimming away 
normally. 
2. Plasmatic cysts may be formed. Here the Spirochaete is dying, and so is 
not normal. The periplast relaxes and the cytoplasm tends to collect into small 
irregular masses or droplets, which cause local bulgings along the body. I have not 
seen these protoplasmatic aggregations other than in animals in an almost moribund 
condition, when the Spirochaetes, naturally, were under unfavourable conditions_ 
One or two similar plasmatic cysts may occasionally be found under similar 
conditions on a blood Spirochaete.” 
It will be .seen from these descriptions that the condition of which 
I give a figure is somewhat different from anything already observed 
and occurs moreover in a blood spirochaete, in an animal not moribund, 
but more probably as a result of the action of the anti-bodies of the 
host. As Fantham suggests, these rings may be a special degeneration- 
form, due however in this special case to the immune bodies in the 
mouse causing the spirochaetes of relapsing fever to die out. At the time 
