TRANSLATIONS FROM CONTINENTAL JOURNALS. 751 
were equally apt to be infected. There is no better proof 
of the ignorance of the cause of smallpox in sheep than 
the multiplicity of opinions on it, which it would be useless 
to quote. Some authors maintain that the malady may 
spontaneously develop itself; but whatever may be said 
to the contrary, the impossibility of a spontaneous gene¬ 
ration of smallpox in sheep has not been demonstrated; 
moreover, some instances are on record where it has 
broken out in places where the fact of its importation 
could not be established. M. Gayofs observations, made 
in the Haute Marne, give evidence of the possibility of the 
spontaneous manifestation of the malady, which must have 
been of spontaneous occurrence the first time it appeared. 
Nevertheless this malady is almost always introduced by 
contagion, which is effected by the serum contained in the 
pimples or pustules, of which the smallest particle brought 
in contact with a healthy sheep will suffice to excite a mor¬ 
bific action. This contagious principle has only to be brought 
in contact with the skin or the mucous membrane to develop 
itself, and it may be conveyed by every possible means, such 
as all animal and vegetable substances. It preserves its 
dire effects for a longer or shorter space of time, according 
as it is more or less exposed to the air. The ordinary mode 
of transmission of the disease is by direct or immediate con¬ 
tact, by the cohabitation or sojourn of affected individuals 
with the healthy, which is easily effected and as easily ex¬ 
plained for by the rupture of the pustules the matter is brought 
in contact with the skin of healthy individuals, and hence 
the infection of the greater part of the flock. Mediate 
transmission is effected by putting healthy sheep in folds or 
pastures where diseased sheep have been; by travelling over 
the same roads; by butchers, shepherds, and other indivi¬ 
duals, after having handled diseased sheep; by dogs, birds, 
litter, dung, &c. It has been remarked that the increase of 
the malady is somewhat peculiar ; at first onty a few of the 
infected flock are attacked, then some others in their turn, 
and so on until about one third have been attacked, when 
the malady seems to become latent for a time, then shows 
itself afresh, until the whole have had it. This seems to depend 
on the fact that the disease is only transmitted by contact at 
the time of the secretion in the pustules, and not at the time 
of their desquamation, as has been asserted. In the regular 
course of an invasion, for instance, the malady is confined to 
a small number of sheep, and is often very slight, because the 
emanations are not considerable, and affect only a few indivi¬ 
duals; but after this first period the greater number of the flock 
