THK NATURE OF THE AMERICAN SWINE PLAGUE. 
297 
fectious diseases (aside from the transmission directly from or¬ 
ganism to organism) is, that although the specific cause, in con¬ 
tagious diseases, may retain its vitality and virulence, under fav¬ 
orable conditions, for some time outside of the animal organism, 
still it does not continue its development there, nor does it really 
infect such extra-organismal material. It simply remains at¬ 
tached to it. It does not find the materials and conditions suit¬ 
able to support its life and proliferating activities. It soon ceases 
to be dangerous. It loses its virulent activity and vitality. 
The inficiens of glanders does not retain its virulence over 
forty days when bound upon the nasal discharge, or some other 
material, from a diseased animal. The rinderpest inficiens does 
not retain this activity for over six weeks, if it does as long as 
that. We know little or nothing about contagious pleuro-pueu- 
monia in this regard. 
Medical technology and language are used with utter disre¬ 
gard of the common decency of exactness. 
Nowhere else is this more apparent than in the use of the 
words contagious and infectious. In general, no attempt at any 
logical or scientific differentiation is made. They are used one 
for the other, in absolute ignorance of their true meanings. 
Infectious diseases, or exogenous diseases, are such in which 
the specific cause—the inficiens—finds its source of primary ori¬ 
gin, and support, and the natural conditions suitable to its exist 
ence in extra-organismal conditions ; that is, outside of any ani¬ 
mal organism. 
The earth, compost and such refuse materials offer, in gen¬ 
eral, the conformable physical and chemical conditions to the 
support and development of the inficiens in infectious diseases. 
Vegetable materials grown upon such lands, the earth, or 
refuse itself, the air and water, contaminated from or by them, 
form the chief media by which susceptible animals become in¬ 
fected. 
According to their character, then, infectious diseases must 
be distinguished as : 
Endogenous or contagious, per se. 
Exogeneous or infectious proper. 
