56
(b) Post mortem.
(i) The number of hours that were allowed to elapse between
death and the inoculation.
(ii) The number of hæmatozoa in the blood just previous to
death.
V.—The Quantity of the fluid introduced into the system of the animal,
either by—
(i) Direct injection into the general circulation,
(ii) Gastric ingestion,
(iii) By subcutaneous inoculation„
(iv) By smearing on an abraded surface, or slight cutaneous in-
cision from which no blood escaped.
(J) The latent period in naturally contracted cases.
A most difficult point to clear up, and one which up to the present has not
been recorded, is the latent period of Surra in cases in which it is contracted
naturally. The difficulty can more readily be understood, when it is recognized
that the contagium is in all probability taken into the system of the animal,
together with its forage or water, or perhaps with both ; and that at a subse-
quent period, when the symptoms of disease become evident, the animal may be
in a different part of the country altogether.
On perusal of Case LXV it will be evident to every one, that the four horses,
A, B, C, and D, were in normal health and condition up to the time of their leav-
ing Malabar Hill on March 16th, 1892. On this date A, B, and C were taken
to Pali Hill, Bandora, and were watered from the wells, which at that season of
the year are getting low, and the water dirty and somewhat concentrated, The
animal D was on the same date stabled in the Fort, Bombay. The horses A, B
and C drank the above well water from March 17th to April 14th, from which
date, as the water had been pronounced very bad, it was discontinued and Vehar
pipe water substituted. A, became unwell on the 15th of April (appeared
feverish); on the 26th she was quite well again, and with B and C was taken on
a shikar expedition, during which they were watered at rivers and wells together
with five Sowar's horses. During this period all these animals were exposed to
exactly the same influences with regard to season, climate, feeding and watering,
as A, B and C were. They all worked hard in the sun between April 26th and
May 17th, and during the whole of this period A was unwell, stumbling in action,
feverish and losing condition ; she was therefore not worked so hard as the
others. On May 17th, they were returned to Pali Hill ; A was then feverish and
unwell ; she was driven a short distance, and on her return appeared to be very
bad, and refused food. On the 23rd of May, B (No. LXV) refused her food, and
an eruption broke out over the whole body accompanied by fever, which con-
tinued until the 30th of the month ; between the 4th and 8th of June A and B
showed symptoms of 'Surra' and on the 9th the Surra hæmatozoon was detected
in B's blood, but that of A was free. A's condition continued to get worse, and
on June 14th she was shot. None of the other horses, C, D, or the Sowars'
animals, have shown any symptoms of illness. This points to the fact that the
disease was contracted from the water of the Pali Hill wells between March 17th
and April 14th, a period of twenty-eight days. There can be no doubt that A's
illness commenced on April 15th, after an exposure of twenty-eight days, and
that the first symptom noticed in B's case was the eruption of the skin, which
occurred on the 23rd of May, so that B was exposed to the influence of the
water for exactly the same period, viz., twenty-eight days, as in the case of A ;
but no symptom occurred for a further period of thirty-nine days, so that the
latent period in A was some time within a period of twenty-nine days, whilst
that of B was within a period of sixty-seven days, and further we learn that
all animals, although exposed to the same dangerous conditions, are not equally
susceptible to the contagium ; as in the case of animal C and the Sowars'
horses.