DESCRIPTION OF PLATES. 199 
Even if we do not discover means of destroying 
these disease-producing parasites within the body 
of the sick person invaded by them, we shall know 
where to find them and how to fight them in their 
external habitats; and by destroying the germs 
of disease in the discharges of those sick with 
cholera and typhoid fever, in the expectoration of 
those suffering from diphtheria and consumption, 
etc., we can, no doubt, greatly limit the ravages of 
these diseases. Indeed, it is not too much to pre- 
dict that the time will come when epidemics of 
these preventible parasitic diseases will be consid- 
ered as great a reproach to a community as the 
vulgar external parasites of man are to the in- 
dividual infested with them among enlightened 
people. 
The writer would not be understood as affirming 
that the diseases mentioned have all been proved 
to be parasitic. There is much evidence in favor of 
this view, and in the case of several of the infec- 
tious diseases the demonstration is complete. But 
satisfactory proof is still wanting as regards the 
greater number, and it would be unscientific to 
generalize in the present state of investigation. 
The question is now being studied by the experi- 
mental method by microscopical experts in various 
parts of the world. Germany and France have 
taken the lead in this line of investigation, and 
Government aid has been freely extended to those 
investigators who have contributed the most to 
our knowledge of “disease-germs.” Unfortunately 
the enlightened policy of the French and German 
