May, 1889. 
PRESIDENT S ADDRESS. 
105 
and preserved from the access of germs from outside, it will 
remain for ever almost absolutely unchanged, except for the 
loss of anv volatile constituents. It will not decav. but the 
*/ */ / • 
presence of a single Bacterian germ is sufficient to set up 
nutrescence. The Bacteria do not all work simultaneously 
A. V 
at this operation, but certain species appear successively, 
Bacterium termo being the first. Any proteinaceous substance, 
exposed to the air, is soon attacked by myriads of this species, 
but after a time they nearly disappear or diminish greatly in 
numbers, and their place is taken by other Bacteria, and by 
the Spirilla, or, as they are frequently termed, Vibrios. These, 
again, are succeeded by Monads, until finally the putrescible 
material is exhausted. Each organism lives by appropriating 
to itself the elements that it needs, and it seems that it leaves 
what it does not want in a condition to afford suitable 
pabulum for another species. The action is in general a 
molecular one, although it is possible that, in the case of the 
larger monads, the action may be partially mechanical, as 
stated by Dr. Dallinger. The ultimate result is to reduce the 
complex organic substance with which we started to its 
elements or to simple compounds, which are then free to 
unite again, and form parts of other organisms, perhaps 
higher in the scale of being. It is thus that life is rendered 
continuously possible on this earth. 
The Great Advance. 
The development of the Science of Bacteriology within 
the last decade is one of the most remarkable instances of 
the unexpected that can be found within the whole range of 
human knowledge. When we read of the state of this 
science ten years ago, how few species were then known, how 
little had been discovered about them, what enormous diffi¬ 
culties were found in doing more than merely observe and 
measure those species which were accidentally met with ; 
when we remember the useless and unproductive controversies 
which raged about their specific value, their growth and 
development, and the questions of their spontaneous gener¬ 
ation, and their connection with disease (controversies which 
were useless because sufficient data had not then been accumu¬ 
lated on which to found trustworthy conclusions), and when 
we contrast that state of darkness and confusion with the 
ease and certainty with which a Bacteriologist of the present 
day isolates, propagates, examines, experiments upon, and 
otherwise marshals and directs the almost invisible units of 
the armies with which he deals, we must confess that the 
