108 MICRO-ORGANISMS IN RELATION TO MAN. 
has been shewn that in many cases each particular leguminous 
plant is provided with its own particular micro-organism, 
Thus, it was found that if pure cultivations of the bacteria 
obtained from a pea-nodule or tubercle were applied to seed- 
lings of the pea there was a more abundant fixation of 
atmospheric nitrogen by the seedlings, than if they were sup- 
plied with pure cultures of the organisms from the nodules of 
a lupin or a robinia; whilst similarily the robinia was more 
beneficially affected by the application of pure cultures from 
the nodules of robinia, than by those from the nodules of either 
the pea or the lupin. 
These are but one or two instances of the necessity of 
micro-organismal life for the continuance of the well-being of 
the world; and they show us, that dire as are the effects of 
certain members of the world of the “infinitely little,” yet we 
owe our very existence to the friendly members of the class. 
These are but one or two instances of the necessity of 
micro-organismal life for the continuance of the well-being 
of the world; and they show us that dire as are the effects 
of certain members of the world of the ‘infinitely little,” 
yet we owe our very existence to the friendly members of 
the class. 
Time will not allow me to dwell upon the distribution of 
micro-organisms. They are, as you know, present in myriads 
in the air we breathe, and in the water we drink. They ac- 
cumulate upon all articles in daily use—the coin of the realm 
and bank notes are not free from them. Milk, butter, and 
other articles of daily consumption contain them, and it is 
scarcely too much to say that there is nothing in Nature 
from which micro-organisms of some kind cannot be obtained. 
As previously stated, the march of epidemics follows certain 
definite routes of travel, the infection being carried from place 
to place and disseminated through the air. We cannot con- 
gratulate ourselves too greatly upon the comparative isolation 
we enjoy by reason of the sea which surrounds our country, 
