4 
Spirochaeta 
icterohaemorrliagiae 
who have seen my method will vouch for the truth of my statement that 
“the large field of vision, the ease with which a slide can be thoroughly 
examined, the absence of any eye strain, and above all the remarkable way 
in which the spirochaete (S. pallida ) strikes the eye, have only to be seen to be 
appreciated.” 
It is enough to say here that I use for this purpose an ordinary paraffin 
lamp with an \ inch wick, a small bulls eye, and an achromatic condenser 
used dry, with a central stop which can be rotated in or out of position at 
will, so that one can pass from dark ground to ordinary illumination, without 
even removing the eye from the microscope. I use an 8 mm. (J inch) apo. 
Leitz and generally search with compensating ocular 6, passing if need be to 
ocular 8, 12, or 18. In the case of fresh coverglass preparations the tube 
length of the microscope is about that for which the objective is corrected, 
viz. 170 mm. In the case of stained films I use no coverglass, and, to com¬ 
pensate for this, increase the tube length to 200 mm. 
For the detection of S. pallida or other spirochaetes in blood I examine 
the preparation dry, without a coverglass, but as the kidney emulsion is so 
granular this is impracticable, so in the latter case I smear over the surface 
of the stained film with liquid paraffin, and let this drain off before making 
the examination. 
It will be seen that the condenser is not oiled to the slide, and hence one 
is not troubled by the oil running, or the stage becoming greasy. S. ictero- 
haemorrhagiae can be detected, with practice, at a magnification of only 
about 220 diameters, i.e. when the No. 6 eyepiece is used, but it is often 
necessary to confirm it by placing in either the compensating 12 or 18 eye¬ 
piece, in which case one obtains a magnification of about 400 to 600 diameters 
with the 8 mm. objective. 
SPIROCHAETA ICTEROHAEMORRHAGIAE IN KIDNEY OF RATS. 
The kidneys of 100 common rats (Mus decumanus) killed in Bournemouth 
or in the surrounding country within an area of about eight miles were ex¬ 
amined. The rats were taken indiscriminately and brought to me, generally 
one or two at a time. Nine of them contained S. icterohaemorrliagiae as follows: 
Total number of Mas decumanus examined 100 
Negative Positive 
Town rats 
38 
36 
2 
1 
f A - 
private estate 
11 
6 
B. 
farms (piggeries) 
33 
1 
Country rats 
62 \ 
1 
farms, etc. 
6 
0 
l D. 
farms, etc. 
5 
0 
100 
91 
9 
The letters A, B, C, D signify different country areas. 
What is most striking is that the rats killed on Area A should show such 
a high proportion, i.e. six out of 17, of positives, whilst from Area B, in 
