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At present we have positively no exact evidence of the mode of exit of parasites
from the body; indeed we have no proof that they ever leave the system of an affected
mule. The sodden-looking congested kidneys might at first sight seem to have been
rendered so by the constant passage through them of these active organisms, but the
disease of those organs is nothing more than is ordinarily found as a secondary
diseased state in cases of very high fever or even of prolonged debility. Micro-
scopical examination of the urine has failed to detect anything like the blood organism.
There are manifest objections to testing this fluid by inoculation. So no method
suggests itself to me for settling the important point whether the animal gets rid of the
parasites in the urine. If it does, then that fluid would be a fruitful means of con-
veyance of the disorder which would seem highly contagious, but it is not so. The
liver and bowels are congested in the height of the fever, and the lining membrane of
the stomach is the seat of extensive lesions, probably due to the parasites ; but, in reply
to the question whether the parasites are thrown off through the alimentary canal, we
can only say that search for such minute beings in the contents of stomach and bowels
seems hardly likely to be followed by good results, and on two occasions the gastric
contents and on a third gastric and large bowel contents given per primas vias failed
to communicate the disease. Carter's experimental inoculations of monkeys with saliva
failed, but Ignatovsky's observation of motile nuclei in perspiration would seem to
indicate possible ways of exit of spirilla from man, but we have as yet no data for
discussing this question conclusively in the case of the mule.
4. Affinities.—Some light would be thrown on the changes in form of the parasite
(if such actually take place) if we knew absolutely what position to assign it in the scale
of living beings. There are three positions for which it presents some features of
eligibility ; it may be bacterian, animal, or vegetable. There are certain of the crypto-
gams, as, for instance, the mosses and ferns, which produce motile, highly active, free-
living spores, termed antherozoids ; some of these evanescently active spores may have
pathogenic importance, but little light has yet been thrown on this matter by patholo-
gical research. It may be remarked that many of these antherozoids show quite as
much purpose in their movements as do the organisms of relapsing fever, and, like
them possibly, their production occurs at certain definite seasons, special intervals
being between each brood, and during the intervals all traces of them (as such) being
lost. We have no evidence that antherozoids are capable of direct production of
organisms like themselves. Altogether it is probable that the organism of relapsing
fever is not a vegetable form of life. There are two kinds of animals which it might
be—an infusorian or a nematode. If the ciliae considered by Dr. Evans as possibly
present in the surra organism and the fin-like processes noticed by him also could be
found, there would be some evidence of the infusorian nature of these parasites. But
I have never found the slightest indication of, or necessity for, ciliary processes or
pseudopods in the Burma disease organisms, and Dr. Lewis failed to detect them in the
surra parasite ; so we must consider their presence as " not proven." Next with
regard to nematode characters, its extremely minute size (considerably less than that
of ordinary haematozoa) might lead us to deny that it is a round worm, but this would
be on not sufficient grounds. Its movements might be taken to be absolute proof of
its animal nature, but they are not sufficient, although they, with its ferocious attacks
on the blood elements, make a strong case. But there is a still stronger one in favor
of their bacterian nature. Whether bacteria are animal or vegetable or neither is
still unsettled, but among them we find some of a spiral form, some of which are
remarkable for the characters of their movements which are like those of the
spirillum of man. The similarity of the organisms observed by me in the Burma
disease (and probably also of those of surra as described by Dr. Evans) to those
found in man, in so far as I can judge by figures and descriptions, and the fact
of their, in the same manner, producing relapsing fever, is strong evidence in favor
of the close agreement in position on the scale of living beings between the
spirochoeta obermeieri and the Burman mule organism, which I therefore consider to
be a spirillum but provisionally term a spirilloid. The similarity consists in form,
habits, habitat, movements, and general appearance, as may be inferred especially
from the description in the.current part of the report. The question of the nature of
the organisms, therefore, resolves itself into the general one of " what are spirilla ? "
which I shall not here discuss, but accept the general view that they are spiral bacteria.
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