492 HORSE SICKNESS OF THE CAPE OF GOOD HOPE. 
wliy they should not do so occasionally, as they are at times 
exposed to the very influences which determine its produc¬ 
tion, such as prolonged journeys, travelling at night, chills, 
&c. There are those also vvho believe that the '‘sickness’^ 
depends on a cobwebby appearance of the grass, and that if 
precaution is observed by keeping the horses in the stable in 
the morning until the sun has dispersed this appearance of 
the dewy grass, and bringing them in before the dew falls at 
night, that the losses are much diminished, if not altogether 
prevented, losing sight of the fact that they are thereby pro¬ 
tecting their animals from prolonged exposure to the cold 
night air, wet, &c.; and further, keeping the influence in 
view^ (too much stress cannot be laid on this point) in con¬ 
nection with cold, as being the co-operative powers in the 
production of this peculiar pleurisy, protection by means of 
good sheds or stables must be insisted upon as the surest 
preventative means at our disposal. The accession of frost 
too is looked to with hopefulness, as bringing with it an 
almost certain check to the advances of this '*• destroyer.^^ 
As frost implies an atmosphere comparatively deprived of 
moisture, and as a sign of the termination of the wet season, 
we may fairly trace back the source of horse sickness to the 
formerly prevailing rains and succeeding heavy night dews, 
in which weather also we may find a mechanical reason for 
the proclivity of horses to lung affections; as if a horse is out 
all night, he will eat all night of the young wet grass, with 
which he gorges himself, the mere mechanical distention of 
his stomach and bowels from the pressure on the diaphragm 
(the muscular partition separating the chest from the abdo¬ 
men) causing at times an oppression of the breathing appa¬ 
ratus, which if unrelieved must produce fatal efiects, from 
the non-escape of gases arising from arrested digestion of the 
extra quantity of grass. Thus those people who keep their 
horses in at night, avoid two evils of great importance; as in 
plentiful times a horse can eat between sunrise and sunset 
much more than he can obtain in twice the time when the 
herbage is scanty from drought. That the horse sickness^’ 
is coeval with wet seasons succeeding drought, is unquestion¬ 
ably proved by reference to the mortality experienced during 
the years 1837, 1854, and 1863, and in reasoning from cause 
to effect, no other conclusion can be arrived at. With regard 
to locality, the mountains were said to possess an immunity 
until this season, when it has been equally fatal there as in 
the plains. No doubt marshy places, low ground, and the 
vicinity of rivers, are all favorable to the development of 
the disease, as may be understood from the misty vapours 
