49
At Dera Ismail Khan (elevation 571 feet) and Kohat, both on the North-
western Frontier the rainfall is small, about 8 inches, the relative humidity has a
mean of about 50, the temperature varying between a mean maximum of 107° F.
in June, and 72° in December, But Dera is situated on the banks of the river
Indus, which is subject to extensive floods during the rainy season, when the whole
neighbourhood becomes one vast lake, and at a later period on the subsidence
of the waters, the land is left covered with. mud.
And lastly Meerut, with an elevation of 7.37 feet, which has a rainfall of
28.5 inches, with a relative humidity of 57 per cent. and a mean maximum tempe-
rature of 112° F.
It will thus be seen from the foregoing details, that the localities in which
Surra is endemic belong to two distinct kinds of climates, The one with a heavy
rainfall, high temperature, and humid, steamy atmosphere ; the other with a dry
arid neighbourhood, presenting a great annual range of temperature. But in both
classes of localities, inundation of land during the rains leaves the fields covered
with mud at a later date, and evaporation and concentration of the water in the
tanks during the hot season.*
2. Residence in a locality where the disease is endemic.
Table IX shows the length of residence in Bombay of eighty animals, the
subjects of Surra, which have been worked out and tabulated from exact details
kept by the Tramway Company. From these figures it will be observed, that
the residence of the animals attacked ranged over a period of from under one
year to thirteen years, and that out of this number the largest proportion,
viz., 16.25 per cent. occurred in animals which had only been in the country for
varying periods of under one year. Further it will be seen, that sixty-one
out of the eighty cases of animals brought forward, or 76.25 per cent. succumbed
within the first seven of the fourteen years under observation.
TABLE IX.
Showing the length of residence in Bombay of 80 horses from the date of purchase
to that of their being attacked with Surra.
1888... ...
1889... ...
1890... ...
1891... ...
1893... ...
Percent-
age...
Under
1
year.
1
8.
1
...
3
13
16.25
1 year
and
tinder
2 years.
2
6
...
...
1
8
10.0
2 years
and
under
3 years.
1
2
...
1
1
5
6.52
3 years
and
under
4 years.
...
6
1
...
3
10
12.5
4 years
and
under
5 years.
4
6
...
...
1
10
12.5
5 years
ami
under
6 years.
4
4
...
...
8
10.0
6 years
and
under
7 years.
...
4
...
...
3
7
875
7 years
and
under
8 years.
...
1
...
...
1
2
2.5
8 years
and
under
9 years.
...
...
...
...
1
1
1.25
9 years
and
tinder
10 years.
2
...
...
...
...
2
2.5
10 years
and
under
11 years.
...
6
...
...
...
6
7.5
11 years
and
under
12 years.
...
4
...
...
1
5
6.25
12 years
and
under
13 years.
...
...
...
...
1
1
1.25
13 years
and
under
14 years.
...
2
...
...
...
2
2.5
Total.
14
47
2
1
16
80
100 .00
3. Months of the year.
Table X shows the number of cases of Surra, which have occurred in the
Bombay Tramway Stables during the past five years, together with a few cases
which have been received at the Laboratory Hospital from other sources, since
October 1890.
From this it will be seen that out of a total of 85 cases, 84 or 98.8 per cent.
occurred during the months of September, October, November and December
The remaining case, or 1.17 per cent., originated in May. Other sporadic
cases, however, have come under our notice during the remaining months, but
they only tend to emphasize the fact, that the disease is chiefly prevalent during
the last four months of the year, and as a rule, after the end of January, few
cases will be found until the last month of the rains.
* Blauford.—Climates and Weather of India, 1889.
B 1086—13