NINTH ANNUAL YEAR BOOK— PART X 419 
and sanguineous temperament, and to superinduce the lymphatic. Other 
foods act by leading to constipation and other disorders of the digestive 
organs, thus impairing the general health; hence in any animal predis- 
posed to this disease, heating, starchy foods, such as maize, wheat, and 
buckwheat, are to be carefully avoided. It has been widely charged that 
beans, pease, vetches, and other leguminosae are dangerous, but a fuller 
inquiry contradicts this. If these are well grown they invigorate and 
fortify the system, while, like any other fodder, if grown rank, aqueous, 
and deficient in assimilable principles, they tend to lower the health and 
open the way for the disease. 
The period of dentition and training is a fertile exciting cause, for 
though the malady may appear at any time from birth to old age, yet 
the great majority of victims are from two to six years old; and if a 
horse escapes the affection till after six there is a reasonable hope that 
he ^\ill continue to resist it. The irritation about the head during the 
eruption of the teeth, and while fretting in the unwcnted bridle and col- 
lar, the stimulating grain diet and the close air of the stable all combine 
to rouse the latent tendency to disease in the eye, while direct injuries 
by bridle, whip, or hay seeds are not without their influence. In the 
same way local irritants, like dust, severe rain and snow storms, smoke, 
and acrid vapors are contributing causes. 
It is evident, however, that no one of these is sufficient of itself to 
produce the disease, and it has been alleged that the true cause is a 
microbe, or the irritant products of a microbe, which is harbored in the 
marshy soil. The prevalence of the disease on the same damp soils which 
produce ague in man and anthrax in cattle has been quoted in support of 
this doctrine, as also the fact that the malady is always more prevalent 
coeteris paribus. In basins surrounded by hills where the air is still and 
such products are concentrated, and that a forest or simple belt of trees 
will, as in ague, at times limit the area of its prevalence. Another argu- 
ment for the same view is found in the fact that on certain farms irri- 
gated by town sewage this malady has become extremely prevalent, the 
sewage being assumed to form a suitable nidus for the growth of the 
germ. But on these sewage farms a fresh crop may be cut every fortnight, 
and the product is precisely that aqueous material which contributes to 
a lymphatic structure and a lovv' tone of health. The presence in the 
system of a definite germ has not yet been proven, and in the present 
state of our knowledge we are only v/arranted in charging the disease to 
the deleterious emanations from the marshy soil in which bacterial fer- 
ments are constantly producing them. 
Heredity is one of the most potent causes. The lymphatic constitution 
is of course transmitted and with it the proclivity to recurring ophthalmia. 
This is notorious in the case of both parents, male and female. The ten- 
dency appears to be stronger, however, if either parent has already suf- 
fered. Thus a mare may have borne a number of sound foals, and then 
fallen a victim to this malady, and all foals subsequently borne have like- 
wise suffered. So with the stallion. Reynal even quotes the appearance 
of the disease in alternate generations, the stallion offspring of blind 
parents remaning sound through life and yet producing foals which fur- 
