1892.] Some Uses of Bacteria. 997 
gets nitrogen out of the air and stores it up in its roots. The 
next season you plow the roots into the soil, and then come the 
nitrifying bacteria which pull the roots to pieces and decom- 
pose them into the condition of nitrates, and then the next 
season the plant which you sow gets hold of the nitrates which 
came from the roots of the clover and which has been brought 
there through the agency of these bacteria. You see, then, 
that the farmer owes everything to the bacteria. 
I think you will find that I am justified in the statement I 
made at the beginning that the study of bacteriology to-day is 
even more truly a department of agriculture than of medicine. 
The bacteria belong to the farmer more truly, or at least as 
truly, as they belong to the physician. 
Now I must draw my remarks to a close. Let me, in con- 
clusion, say that we must not think too hardly of bacteria. 
It is true they are the causes of evil, it is true that they produce 
disease, but it is also true that they do good. It is true that 
they are our enemies but it is also true that they are our closest 
allies. It is true that without them we could not have our small- 
pox nor our yellow-fever, we could not have our diphtheria or our 
scarlet fever, neither could we have the epidemic which is at 
present going over this country, nor in fact should we have 
any of our epidemics were it not for the bacteria. But when 
we remember that it is through the agency of these organisms 
that we bake the loaf of bread that comes onto our table, that it 
is through their agency that the immense brewing industries 
are able to exist, that it is through their agency that the 
industries connected with the manufacture of alcoholic liquors 
are possible; that without them we could not get our vinegar 
or our lactic acid; that without them we could not make our 
ensilage; when we remember that these bacteria give the 
butter-maker the aroma of his butter; when we remember 
that it is the decomposition products of the bacteria that the 
cheese manufacturer sells in the market; when we remember 
their agency as scavengers, how it is that they keep the sur- 
face of the earth clean and fresh and pure and in a constant 
condition for the continued growth of plants; when we 
remember their value to the soil in decomposing the dead 
