FRANK S. KILLINGS. 
must stick to it, that a coutagious disease is one which has its 
primary origin within or upon an animal organism, and never 
outside of it. The manner of transmission is a matter of no im¬ 
portance whatever in deciding this question, so far as it has ref¬ 
erence to any form of inoculation. 
Contagious diseases are transmitted from organism to organ¬ 
ism, both by direct and indirect (cohabitation) contact. 
Infectious diseases infect the animal organism by its being 
exposed to a common cause in the surroundings. They are never 
transmitted from a diseased to a healthy organism directly, or b} T 
cohabitation, except by the accidental presence of some interme¬ 
diate conveyance. 
The diseased organism simply plays the part of a local con¬ 
veyance (or center) of infection, which offers favorable conditions 
for the transitory development of the inficiens, but in which it 
never develops primarily. 
Had we telleological views of life, we might say that the 
micro-organismal enemies of life selected that life to be the 
means of spreading the means to its own destruction, but I don’t 
believe any such nonsense. 
In order to make my meaning still more evident, we will turn 
our attention to that decidedly infectious and manifestly non- 
contagious disease, Texas fever, the twin-sister to the yellow 
fever of our own species. 
Like the swine plague, this is a local—or telluric—disease, 
capable of being temporarily transmitted to our northern pas¬ 
tures by Texan cattle, but, unlike swine plague, it seems incap¬ 
able of withstanding our northern winters, and hence it soon 
dies out. 
The Texas cattle seem to have become acclimated to it, but 
are none the less dangerous to our northern pastures, though 
scarcely any symptoms of illness may be seen in them. 
I repeat, infected Texans are not, in or of themselves, at 
all dangerous to more northern cattle. The latter may breathe 
the same air with them, even lick them, in fact may be only sep¬ 
arated from the Texans by a wire fence, and remain healthy ; 
but if we remove the Texans and put the natives on the same 
