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ever, that no case of surra occurs in which the infusorian is absent; that blood containing it
will invariably induce surra; that after passing it through the blood of various animals and
again inoculating it to the horse, surra results; that surra blood, deprived of its formed
elements by filtration, will not cause the disease on inoculation; and lastly, that the presence
or absence of the infusorian in the blood influences the course of the disease to a very marked
degree, dividing it into its various stages, viz., paroxysms and intermissions.
Contagion.—Surra does not appear to be contagious in the ordinary acceptation of the
term; the contagium is neither conveyed by the air nor under ordinary circumstances by the
sick to the healthy; but at the same time it must not be forgotten that an animal suffering
from the malady must be a source of danger, owing to blood-stained discharges contaminating
the food and water consumed by healthy animals: for we know that the ingestion of blood
containing the infusorian causes the disease. The sick are especially dangerous when they
are kept near animals which have wounds, for it has been proved by experiment that the
fraction of a minim of soiled blood containing the infusorian, placed between the edges of a
minute wound in the cuticle, is sufficient to reproduce the disease in seven days.
Latent period.—This varies with (1) The species of animal inoculated; (2) means
used for inoculation; (3) the material used; (4) whether the material is taken anti or post
mortem; (5) the quantity of material introduced. The extreme irregularity of the latent
period is shown to vary from one to 75 days. For the report the symptoms are thoroughly
dealt with and analysed, as are also the stages of the disease. The microscopical lesions are
also noticed at length, but the miscroscopical examination of the tissues has yet to be dealt with.
Treatment.—The treatment of the disease has been undertaken and various therapeutical
agents have been employed with a view to the destruction of the infusorian in the system:—
Mercuric chloride has been employed subcutaneously and also by direct injection into
the circulation, with negative results.
Iodine and iodide of potassium by intertracheal and also by subcutaneous inoculation
were followed by negative results.
Iodoform, by subcutaneous injection and also by direct injection into the jugular produc-
ed no good results.
Oleum terebinthinæ by subcutaneous injection and by injection into the jugular, was
followed by negative results.
Potasi bichromas directly injected into the circulation produced no marked effect upon
the infusorian.
Mixed cinchona alkaloids and arsenic did not destroy the infusorian.
Carbolic acid and iodine—76 drachms of the former and 34½ drachms of the latter—in
six days produced no apparent effect on the infusorian.
Quinine in large doses has no effect on the infusorian.
Iodic hydrarg, a very powerful antiseptic, had no effect.
Santonin had no effect.
Potass had no effect.
Arsenic.—The administration of this agent is undoubtedly followed by a marked
effect on the mature form of the infusorian; for after a quantity of it has
entered the system, the crops of infusoria do not appear in the blood as they do
in cases which have not been treated with it. In one case treated, the mature
infusorian was absent from the blood for 84 days, and the system appears to
react in a marked manner, at first to the drug with regard to the effect of
arsenic on the hæmatozoon, therefore, it doubtless exerts some influence prejudi-
cial to its development, as can be seen on consulting the charts of horses, in the
treatment of which it had been used; but so far as the report shows it appears
probable that the infusorian may exist in the immature form and continue to
cause mischief which prevents recovery. That the absence of the mature
organism from the blood of an animal is not a certain sign that it is destroyed
will be gathered from the experiments made with the blood of a bull. In this
case, although no mature infusoria were observed in the blood after the first
paroxysm, the inoculation of the bull's blood taken at periods varying from S5
to 163 days, from the date on which the parasite had disappeared from the
blood, was followed by positive results; the animals, the subject of inoculation,
perishing from surra. It is not therefore beyond the range of possibility that
although no mature infusoria could be detected in the horses treated with arsenic,
the immature form, which has not yet been recognised, may have remained
present; and that although the system reacted to arsenic, and some ameliora-
tion of the symptoms occurred, the effects were not sufficiently energetic to
completely overcome the mischief caused by the mature parasite—that which
might arise from the presence of the immature form; so that the progress of
the disease, although checked, continued towards a fatal termination. It seems
more likely that this should have been the case, than that the animals should have
succumbed to the poisonous action of arsenic; for the majority of cases do not,