57
In Horses.
Thus horse A drank polluted water between the 17th March and April
14th, 1892. First symptom April 15th 1892. Latent
period some time within a period of twenty-nine days.
Horse B. (No. LXV) drank polluted water between the 17th March and
April 14th, 1892. First symptom, urticarial eruption, May 23rd, 1892. Latent
period some time within a period sixty-seven days, but certainly not less than
thirty-nine.
(II) The latent period, when the contagium is given by the mouth :—
(a) Gastric ingestion of a considerable amount of soiled blood,
(6) In small doses in water, following more closely the way in which
animals are supposed to contract the disease naturally.
(a) By gastric ingestion of a considerable amount of soiled blood.
On the evening of September 29th, 1880, Evans* experimented upon a fairly
healthy, aged, mare, by administering twenty ounces of blood drawn from the
Jugular Vein of an animal suffering from Surra. On the morning of October 6th,
the blood when examined microscopically was swarming with very active
parasites. In this case an observation was made on the 4th of October, to
the effect that the temperature was 99.8°F. (37.6°C.); blood examined, but no
parasite found ; but there is no note on the following day, the 5th, regarding the
condition of the blood, although the temperature is recorded as having been
102.2°F (39°C). Consequently I am inclined to believe, that the hæmatozoon
would have been found on the 5th if it had been looked for, taking into account
the rise of temperature and the fact that the hæmatozoa were swarming in the
blood on the morning of the 6th. In this case then, the latent period may be
said to have been only 5.5, or at the most 6.5 days.
On the morning of the 30th of September, to a second mare Evans gave
twenty ounces of blood, drawn from the Jugular Vein of the same horse, as
that from which the blood was taken for the preceding experiment. On the
morning of the 6th of October, with a temperature of 103 0 F (39.4 0 C) the
blood presented many parasites, but not swarming as in the last case. The
latent period extended from the morning of the 30th September to that of the
6th October, or six days.
(b) By giving small repeated quantities of soiled blood in water.—As no
previous researches have been conducted with small quantities of soiled blood
in water, it was decided to endeavour to produce the disease, in a somewhat
similar manner to that in which it is naturally contracted. With this end
in view, a strong healthy Australian gelding was obtained, 16 years old
and in good condition, to which small quantities of blood mixed with a large
bulk of water were to be given at short intervals. Accordingly on the 4th May
1891, four minims (0.25c.c.) of blood, (swarming with the Surra hæmatozoon),
mixed with one gallon of fresh water, were given to the animal to drink. Up to
the 9th no change had taken place in the animal's condition, and on this date
eight minims (0.53c.c.) of blood containing numerous hæmatozoa were given
in the same way. On the 10th and 11th the animal showed no change. On the
latter date six minims (0.4c.c.) of blood containing the Surra hæmatozoon were
given in a quart of water. On the 12th a few small petechiæ were noticed on
the membranæ nictitantes. Up to the 24th with the exception of a slight in-
disposition on the 18th, which rapidly passed off, no symptoms of disease were
noticed. On the 24th the animal received in water eight minims (0.53c.c.)
of blood containing very numerous hæmatozoa ; no change of any importance
was noticed up to the 6th June, and on that date the animal received in water
eight minims of blood containing numerous hæmatozoa. There was no change
on the 14th of June, when thirty minims (2.0 c.c.) of blood containing very
numerous hæmatozoa were given in three quarts of water. On the 16th no change
having taken place, ten minims (0.66 c.c.) of blood swarming with hæmatozoa
were given. On the 17th twenty-five minims (1.6 c.c), taken from Horse
* Evans—Appendix F.
B 1086-15