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Some doubt as to the close alliance of the mule and man organisms legitimately existed
until both had been stained and examined in the quiescent state; but, now we know
that the former readily take aniline dyes, are curled up subspirally after death, and are
found very like the stained spirochaetes of man as figured by Ziegler, I think we can
have no further doubt on this point, and we cannot consider that the only relapsing
fever of man differs intrinsically and radically in its probable producer from the only
relapsing fever hitherto described as such in equine patients, and that both these fevers
induced by similar means produce a relapsing fever of the monkey in spite of the
radical and intrinsical differences in their causes ! Adherence to this latter view
would argue an incapability of appreciating and accepting such proofs as are generally
acknowledged to be sufficient in natural history and modern pathology. Indubitably
the nearest allies of these mule organisms as well as of those which Dr. Evans
found in the disease called " Surra " are the " flagellated organisms " found in the
blood of rats and some other rodents, not known to be diseased, of which Dr. Lewis
says they " present many features in common with motile organisms undoubtedly of
vegetable origin; on the other hand, taken as a whole, they appear to approach more
closely to the forms of life usually classified as protozoa * * * *. Many believe
that these organisms are zoospores, and not animalcules" (vide his " Microscopic
Organisms found in the Blood of Man and Animals "—Calcutta, (1879).* Koch's
cultures of spirochæta, whereby he obtained long spiral organisms, open a fresh line
of inquiry, which will possibly be in the future the means by which we shall learn
exactly the relations which spiral organisms of pathogenic nature found in the body
bear to those similar bodies found in marshes and to spiral organisms as those of the
teeth not known to be pathogenic. Hitherto these relations have been extremely
problematical, but elaborate culture and working with the higher powers will in due
course solve the mystery.
5. I may summarise the PRINCIPAL RESULTS OF THE INQUIRY as follows :—
Positive: (1) The unusual fatality among mules in Burma is due to a disease
which is not poisoning, nor ulceration of the stomach, nor simple fever,
nor simple anæmia.
(2) The disease in question is a true relapsing fever, probably the first ever
recognized as such affecting equine patients.
(3) It is essentially the same as the disease described in 1880 by Dr. Evans as
" surra," and only differs from it sufficiently to warrant our considering
them (for the present) as local varieties of the same disease.
(4) It is allied to relapsing or famine fever of man, but more distantly.
(5) These allied disease states have been carefully compared.
(6) In the blood in each is found an organism; those described as occurring
in the three disease states differ more or less markedly in various
respects.
(7) Their nature has been examined, and it is concluded they are spiral
bacteria.
(8) Their detection, actions, and relations to the phases of the Burman disease
have been demonstrated and compared with those of the other disease
states.
(9) Their relations to the affected animal are in exact accordance with the
fever phases, so much so as to render the diagnosis of relapsing fever by
aid of the microscope and thermometer and graphic records a matter of
absolute certainty.
(10) The reasons for obscurity in diagnosis hitherto have been carefully
demonstrated.
(11) The symptoms of the disorder have been carefully observed and recorded.
* Dr. Carter has demonstrated Lewis' rat organisms since the above was written. They certainly in actions and
appearance resemble the organisms of the mules. In the rat they seem to inhabit the blood as " messmates " with the
red corpuscles without exhibiting an aggressive policy towards the latter. In stained specimens they seemed to have
shorter tail portions and bodies more uniform in diameter. The rats looked healthy, but no temperature records of them
have been yet recorded on a chart (3rd July 1885). I have inoculated a horse with some rat's blood containing organisms,
local tumefactions occurred but no systemic invasion; in fact, results similar to those obtained by introduction of the mule
organism into the ox were found in this experiment. The rat, kindly sent to me by Dr. Carter, was certainly unhealthy,
his toes sloughing. This may have been due to confinement, but it reminded me of my experimental monkey (18th
August 1885).