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on sedgy vegetation, so that we are unable to state with certainty that
these media really do convey the materies morbi. It is possible that
the infusorian does not exist in its mature form in either of these
media, but that there may exist an immature form which has not yet
been recognised. The excreta of rats has been blamed by some as a
possible medium, and no doubt on good grounds, for we know that
an infusorian apparently identical with that found in Horse Surra is
very frequently found in the blood of these animals, and that this being
the case, should any of the blood be passed with the fæces or urine, it
would be quite possible that surra might be induced in horses which
consumed them with their forage. Be this as it may, in Poona it has
been found impracticable to induce "Surra" by feeding horses with a
considerable amount of dung obtained from rats, in whose blood the
infusorian is present in large numbers (swarming). The infusorian can
be absorbed into the circulation from the digestive system, as has been
proved by giving small quantities of blood containing it in the drink-
ing water.

Contagion.—From the evidence we have at hand it would appear
that surra is not communicable by the sick to healthy animals, except
under certain conditions. The disease is not contagious in the ordinary
acceptation of the term. The contagium is neither conveyed by the
air, nor by the sick to the healthy, but gains an entrance with the food
and water, or is introduced by some form of superficial inoculation; and
it is necessary for one or other of these two forms of inoculation to
take place, in order that the disease be successfully transmitted.

The blood of an affected animal when introduced subcutaneously into
a healthy one, possesses the power of reproducing the same disease
whether the infusorian at the time of its withdrawal be capable of demon-
stration by microscopical means or not. As regards the quantity required,
it has been fourd that the fraction of a minim of soiled blood, containing
the infusorian, placed between the edge of a minute wound in the
cuticle of a healthy horse, was sufficient to reproduce the disease in seven
days.

Possibility of Contagion.—Taking into consideration the above
fact, it is easy to understand that there is some danger of the disease
being transmitted by the bites of certain flies, especially by blood suckers
armed with borers, for it is quite possible that a certain number of
the infusoria may be carried on the proboscis and inoculated into
healthy horses, specially when they are kept close together.

With the knowledge of the fact that a small quantity of blood in
water may, when swallowed, induce the disease, we may consider it
possible that the discharge from a sick animal, if containing blood, may