are, however, most certainly and speedily developed in
circumstances inimical to general good health, and often occur
at certain, so called, critical periods of life, when unusual
demands on the vital powers take place.

6. They show a striking tendency to modify and absorb into
themselves all extraneous diseases; for example, in an animal of
consumptive constitution, pneumonia seldom runs its ordinary
course, and when arrested, often passes into consumption.

7. Hereditary diseases are less effectually treated by ordinary
remedies than other diseases. Thus, although an attack of
phthisis, rheumatism or opthalmia may be subdued, and the
patient put out of pain and danger, the tendency to the disease
will still remain and be greatly aggravated by each attack.

In horses and neat cattle, hereditary diseases do not usually
show themselves at birth, and sometimes the tendency remains
latent for many years, perhaps through one or two generations
and afterwards breaks out with all its former severity."

The diseases which are found to be hereditary in horses are scrofula,
rheumatism, rickets, chronic cough, roaring, ophthalmia or
inflammation of the eye,--grease or scratches, bone spavin, curb, &c.
Indeed, Youatt says, "there is scarcely a malady to which the horse is
subject, that is not hereditary. Contracted feet, curb, spavin,
roaring, thick wind, blindness, notoriously descend from the sire or
dam to the foal."

The diseases which are found hereditary in neat cattle are scrofula,
consumption, dysentery, diarrhea, rheumatism and malignant tumors.
Neat cattle being less exposed to the exciting causes of disease, and
less liable to be overtasked or exposed to violent changes of
temperature, or otherwise put in jeopardy, their diseases are not so
numerous, and what they have are less violent than in the horse, and
generally of a chronic character.

Scrofula is not uncommon among sheep, and it presents itself in
various forms. Sometimes it is connected with consumption; sometimes
it affects the viscera of the abdomen, and particularly the mesenteric
glands in a manner similar to consumption in the lungs. The scrofulous
taint has been known to be so strong as to affect the foetus, and
lambs have occasionally been born with it, but much oftener they show
it at an early age, and any affected in this way are liable to fall an
easy prey to any ordinary or prev