THE NATURE OF HUMAN TICK-FEVER 
127 
Ticks are not without natural enemies. Rats eat adults with avidity, 
and ants carry off young ones and eggs. We have lost ticks in both ways. 
On one occasion over two hundred young ticks were carried off in a single 
night by small ants. 
We add the following scanty working notes on the anatomy of Ornitho- 
doros, and on the presence of spirochaetes in its organs, in the hope that they 
may be useful to others interested in this subject. 
There is a most curious piece of anatomy in the adult tick which, for 
want of a better name, we have termed the (?) " pulmonary sac t " Just above 
the base of the proboscis is a slit which communicates with a wide mem- 
branous tube ending in a paired body, or, rather, a closed sac, whose walls 
are at first thin, near its attachment to the tube, and distally are thickened 
and thrown into folds. The accompanying diagram (PI. 4, fig. 1) illustrates 
this point. 
It is curious that we have never seen these ticks excrete dark-coloured 
faecal matter. It is always white-coloured secretion of the malpighian tubules 
which is passed by the anus. This fact may, in some part, be explained by 
the exceeding fineness of the tube running from the under surface of the 
" stomach " to the central cul-de-sac of the cloaca. The diagram (PI. 4, fig. 2) 
is very schematic, but it will serve to illustrate the course of the alimentary 
tract. 
The position and rough structure of the salivary glands are indicated in 
a diagram (PI. 4, fig. 3). The appearance of the salivary duct is very 
characteristic. 
A batch of ticks caught at Nyangwe (November 23rd, 1904) were fed 
upon one of our infected monkeys. They were kept without further feeding, 
and one was dissected every day or two. Living spirochaetes were found in 
their stomachs and malpighian tubules up to five weeks after their feed on a 
known, infected animal. (It must be remembered that these ticks were 
naturally-infected adults.) Occasionally very many more spirochaetes were 
found in the tubules than in the stomach. In some preparations of stomach 
or malpighian tubules no parasites were at first seen ; but if a little human 
serum, taken from one who had never had tick fever, were added, in from 8 
to 24 hours the preparations became fairly crowded with spirochaetes. 
As we have noted on page 13, we have so far been unable to follow out 
111 these ticks Schaudmn's masterly observations. We have also been, up to 
the present, unable to find in the bone-marrow, spleen juice, or blood of 
monkeys or human beings infected with these spirochaetes forms resembling 
the large macro- or microgametes, described by Schaudmn 111 his work. 
From the facts here presented we conclude that: — 
(1) . Tick fever is clinically identical with relapsing fever, and 
has for pathogenic agent a spirochaete. 
(2) . The spirochaete is probably Spirochaete Obermeieri. 
(3) . The tick, Ornitkodoros moubata, can transmit the spiro- 
chaete from animal to animal. 
(4) . The transmission is not merely mechanical, but some 
developmental process is carried on in the tick. 
(5) . A considerable degree of immunity or tolerance to the 
spirochaete can probably be acquired. 
* March 28th, 1905. We have just seen two other European cases. 
