CRAP Te xX. 
CAUSES OF -— DISEASE. 
Inflammation and Fever.—Thus far we have been con- 
cerned with diseases and malformations arising mainly 
from structural alterations due to the combined effects 
of variability and inheritance. We will now consider 
some examples of disease due to other causes. 
Biological researches of the last few years have shown 
that many diseases of animals are due to the entrance, 
and subsequent multiplication in the system, of micro- 
scopic bodies known collectively as bacteria, or micro- 
organisms. It has been clearly established by an 
overwhelming amount of evidence that such conditions 
as tuberculosis, glanders, actinomycosis and_ other 
contagious diseases are due to the action of these 
minute bodies. 
For our purpose bacteria may be divided into two 
groups—those which when introduced into the body 
cause no harm, and those which produce disturbance 
either local or general. The latter are said to be 
pathogenic, or disease-producing. A study of the 
relation of bacteria to disease is of great interest, and 
sheds abundant light, not only on the nature of specific 
diseases, but also on the nature of a very remarkable 
condition known generally as inflammation. 
