558 
ON THE EXTERNAL CAUSES OF DISEASE. 
This species of attraction has been called a new power. It is 
a power that enables the atmosphere to attract suddenly, and 
with force to windward, and to a considerable distance from the 
spot whence they originate : indeed, such is the surprising force 
of the power, that metallic particles are in some instances attracted 
by the air, as persons of weak constitutions have been affected 
with mercury merely by sitting for a few hours near those who 
were in a state of salivation. 
Mr. Youatt, in his lectures delivered at the London University, 
mentions an epidemic which prevailed in the year 1815; and so 
dreadful and sweeping was the disease, that three horses out of 
five that w^ere attacked died. 
Among neat cattle its ravages are too notorious, and its 
characters too well marked to need any description : "‘and it may 
be considered,” says Mr. Blaine, “ as a full proof of the liability 
of the horse to the same, it having occurred, that, during the 
ravages of the malignant epidemic among cattle, horses have 
also become affected; though it must be allowed that this has 
seldom taken place,” and, on the contrary, in some seasons there 
has been undoubted evidence that horses have fed and housed 
among infected kine with impunit 3 ^ But that, not only does the 
horse generate and produce the epidemic with a true malignant 
character in his own person, but that he does also now and then 
receive it by the medium of affected cattle, there is also full proof.” 
The different ancient authors support Mr. Blaine in his opinion. 
Lucretius, who describes the plague of Athens, speaks of a ma¬ 
lignant epidemic disease affecting almost everj^ animal. Homer 
likewise describes one of these dreadful scourges, as attacking 
men and animals indiscriminately at the siege of Troy. 
»\ «/ 
- (jLSTOCO IQV iVifCS 
Ahjvv? Ji’hotyy^ yeviT a^yv^soio jSioTo. 
TT^uTov i'rruyi'vo, xa) Kvva,<; cc^yov^, 
AvTu§ gTTElT UVroTi7t 
But the most interesting account of these sweeping diseases 
is one that occurred throughout Germany and Italy, described by 
Virgil*. 
See Georgies iv. 
