A. C. Coles 
7 
is a fine point, but no minute flagellum-like projection could be demonstrated 
by staining (Loeffler, Pitfield, Casares-Gil, Fontana, etc.) or by dark ground 
illumination. It is devoid of a terminal filament such as is characteristic of a 
Spironema or Treponema and is resistant to saponin (10 %) unlike all other 
spirochaetes. It calls for a new genus, and on account of its fine and minute 
windings the name Leptospira is suggested.” 
I found that the fine spirals could be seen in preparations made by mixing 
a small drop of the kidney emulsion with Congo red and then treating the 
dry film with 1 % HC1 alcohol, a method described by Benian (1916), but T 
seldom obtain a good preparation of any spirochaete with this procedure. 
The photomicrographs (PI. I) at various magnifications, illustrate the 
spirochaetes in the blood of the experimentally inoculated guinea-pig and in 
the kidney of naturally infected common English rats. Here the minute 
spirals can be clearly seen. That the rat spirochaetes are morphologically 
identical with the S. icterohaemorrhagiae of the guinea-pig, there can be no 
question, as the photographs were taken at precisely the same magnification 
and under absolutely the same conditions, and even on the same quarter-plate. 
In Japan, in Flanders and in America, both in New York and quite 
recently in the Southern States, pathogenic spirochaetes have been found in 
the kidney of the ordinary rat, and in all these countries cases of Infectious 
Jaundice are knowm to occur. 
Now in England I find identically similar spirochaetes in 9 % of the 
rats killed in the town and surrounding country. It is highly improbable 
that these rats have only recently become infected by soldiers w r ho have 
returned home convalescent from Weil’s Disease, as some of the infected rats 
came from remote country villages. The question naturally suggests itself: 
does so-called Weil’s Disease or Infectious Jaundice occur in England? 
The articles dealing with the disease in Allbutt’s System, the Encyclopaedia 
Medica, Osier and Taylor’s Medicine, and the more recent communications 
in the Medical Journals do not definitely state the fact, but all agree in associ¬ 
ating the disease with insanitary surroundings and with especially such 
occupations as slaughtermen, sewermen, butchers, etc., which are just those 
in w r hich the rat comes in the vicinity of man. 
Spirochaeta morsus muris. 
During the whole of the investigations on rat spirochaetes I have not only 
searched for S. icterohaemorrhagiae, but other forms have been looked for, 
especially that which the Japanese w T orkers have now proved conclusively is 
the cause of rat-bite fever. But it was not till I examined the kidneys of the 
84th rat, one sent in from the country district B, a half grown rat measuring 
inches, that I met wdth a short, rigid, and thick spirochaete which T have 
little doubt may be the spirochaete of rat-bite fever. 
I have measured 65 spirochaetes and find the average length to be 5-45/z 
with 2*2 curves. Tw t o types w r ere seen, one a shorter spirochaete ca. 4 to 5p, 
