puesident’s address. 
295 
of their presence and reproductive activity, — either as cause, or as 
an accompaninient of these disease manifestations. And this 
applies not only to the liunian species, but to lower classes of 
animals, between whom and man many of these diseases are 
interchangeable. 
Such knowledge necessarily invests the life history of these 
minute Germs with intense interest, seeing that it is probably one 
step, and that a long one, towards the discovery of the means of 
prevention, if not also of cure, of many of our most fatiU and 
dreailed diseases. 
E.\amples of such diseases are : — Scarlet Fever, Diphtheria, 
Small Pox, Cholera, Yellow Fever, Tuberculous Disease, Ague, 
Hydrophobia, Cattle Plague, Anthrax; and many others might be 
enumerated whoso dependence upon parasitic Germs is almost 
conclusively jwoved. But these are sullicient to show the deep 
interest of this branch of study. 
Not only are these Germs found in the solids of the body in 
some of these diseases, but in others their presence is easily and 
constantly recognizable in the blood or other fluids, and even 
within the corpuscles which the blood so largely contains. And 
not only so, but the forms which these micro-organisms present are 
so constant and so definite in the dilfercnt disorders, that it is now 
almost iiossible in some instances to diagnose what diseased 
condition wo have to deal with by an examination of the fluid 
or tissue in which they are contained. 
It is, perhaps, but right here to say that some of our most 
cautious observers consider that it is as yet hardly proven that the 
dill'ering Germs found in the various diseases are their actual and 
efficient cause ; but their definiteness in the various disorders, and 
the constancy of their presence, leave little doubt that this Avill 
hereafter bo conclusively shown to be the case. 
Some of these Germs seem to have a short life and rapid 
development, and then we have acute disease. Others seem to 
have a more prolonged or continuing career, and then we have 
chronic disease. "Whilst others seem to have an intermitting 
development, and then we have paroxismal disease. 
