of twenty-three head, of which seven
died; of twenty-two head, of which eight died; of twenty-two head, of
which eight also died; and of twenty-one head, of which four died. A
little less than thirty per cent., therefore, of these herds died.

This estimate excludes the calves. Most of the cows which had not calved
before being attacked, lost their calves prematurely. The probable time
of incubation, as deduced from those Massachusetts cases, is from two to
three weeks; of propagation, about the same time; the acute stage of the
disease lasting about three weeks.

The author's attention was first directed to this disease, upon its
appearance in Camden and Gloucester counties, New Jersey, in the year
1859, at about the same time it made its advent in Massachusetts. The
singularity of this coincidence inclined him for the time to regard the
disease as an epizooetic--having its origin in some peculiar condition of
the atmosphere--rather than as a contagious, or infectious disease,
which position was at that time assumed by him.

This opinion was strengthened by the fact, that no case occurring in New
Jersey could be traced to a Massachusetts origin, in which State it was
claimed that the disease never had existed in this country previous to
its introduction there. It was, therefore, denied by the veterinary
surgeons in the Eastern States, that the disease in New Jersey was the
true European pleuro-pneumonia, but it was called by them the swill-milk
disease of New York City, and it was assigned an origin in the
distillery cow-houses in Brooklyn and Williamsburg.

In 1860 it found its way across the Delaware River into Philadelphia,
spreading very rapidly in all directions, particularly in the southern
section of the county, known as The Neck,--many of the dairymen losing
from one third to one half of their herds by its devastating influence.
In order to save themselves--in part, at least--from this heavy loss,
many of them, upon the first indications of the malady, sent their
animals to the butcher, to be slaughtered for beef. In 1861 the disease
found its way into Delaware, where its ravages were severely felt. So
soon, however, as it became known that the disease was infectious or
contagious, an effort was made to trace it to its starting-point; but,
in consequence of the unwillingness of dairymen to communicate the fact
that their herds were affected with pleuro-pneumonia, all efforts proved
fruitless. In 1860 the dis