47
active parasites are present, the membranes are generally yellow and free from spots.
Although the membranes will not be found to answer this description in all cases, the
typical occurrence of spots is sufficiently frequent to warrant our considering it a fact
in the pathology of the affection. In their active phases the parasites cause irritation
of the membranes as is sufficiently evident from the lachrymation, profuse salivation,
and slight discharge from the female generative passage, but later in their life they
tend to aggregate either by two individuals uniting longitudinally to form a long one
either temporarily or permanently (which is rare), or by several becoming entangled
together to form wriggling masses, which Ignatovsky considers most frequent just
before the crisis. Although each parasite is in diameter smaller than the smallest
capillary, it is not hard to understand how several individual's wriggling together may
block up an extremely narrow passage through which they are trying to pass ; hence
results a more or less persistent plugging of the vessels, which becomes the more wide-
spread because the blood in this disease has a marked tendency to form clots in the
living vessels. Petechiæ, extensive extravasations, dropsies, and even ulceration are
possible, indeed probable, results of such plugging of minute vessels. Ulceration of
the stomach thus or otherwise induced might act as a cause of further or primary
invasion by spirilloids. There can be no doubt that of two animals grazing in a marsh—
one with healthy unbroken mucous membranes, the other with gastric ulcer,—the latter
would be the more liable to invasion by low organisms. Although the stomach lesions
seem to be part of the disease and have been found fresh and actively progressing
where no other possible cause is known to have been in operation, we have to be
careful in deciding that they are not due to medicine administered in the course of
the attack or otherwise or to coarse improperly prepared food; since the lesion is
present in cases which have not been treated and which have been fed on soft, well
prepared food for some months before death, we must look on the gastric ulceration
as a feature of the disease which, on minute examination, seems to result from
plugging of the small blood-vessels of the stomach. Thus the lesions found ante-and
post-mortem in cases of relapsing fever are such as might be, and probably are, caused
by the parasite found in the blood.
9. Thus relapsing fever of mules is an invariably fatal disorder characterised by
the periodical occurrence of attacks of high fever, during which a special organism,
closely resembling that of spirillum fever of man, is found in the blood. The organism
causes disorganization of the blood, which is to an extent repaired during the inter-
paroxysmal phases, and thus the patient is usually able to hold up against the disorder
for some time. But anaemic symptoms and lesions gradually accumulate and culmi-
nate in death from exhaustion, plugging of vessels, or gastric perforation as a result of
local atrophy of the stomach. In some cases the symptoms are acute, and the animal
succumbs to the height of the fever.
PART IV.—THE PARASITE.
It only remains for us to examine the natural history of the characteristic organism
as found in the blood of mules suffering from relapsing fever. We may do this in the
short business-like language of science.
2. GENERAL CHARACTERS—Size.—Varies in different cases; usually 1/6 red corpuscle
in diameter and 3—6 times in length.
Shape and appearance.—In fresh state it is an eel-like body, moving from corpuscle
to corpuscle, or looks like a highly motile flagellum with most varied movements
appended to a red corpuscle and causing agitation of it and of those in the immediate
neighbourhood—dark or refrangent according to focus. In dried state and stained is
found to be very like an oxyuris on a small scale, to have a thick portion of the body
and a spiral tail, the latter taking less of the dye than the former, commencing
as a sudden narrowing of the body and terminating by a fine point although the whole
organ is visible in the living animal and has nothing of the nature of an infusorian
flagellum. The thick portion tapers in either direction from its centre. Anteriorly
it terminates rather abruptly and is somewhat rigid. We have reason to believe there
is some holdfast organ at this extremity. The thick part is as spiral as is compatible
with its diameter. Dr. Evans having examined the live specimens at Rangoon, also the
dried and stained ones I sent him, is of opinion that they are essentially the same kind