JANUARY 25, 1901.] 
parent similarity of the organisms con- 
cerned, the ordinary methods of study and 
of classification are quite insufficient, so 
that new and highly peculiar methods have 
been devised and employed. Bacteriology 
does not depend, as ornithology and ento- 
mology chiefly do, on the external and in- 
ternal anatomical features of individuals, 
but only to a small extent on these, and 
chiefly on the behavior of flocks, swarms, 
groups or masses of individuals, and upon 
these not in a state of nature but artifically 
massed or cultivated. Bacteriology finds 
its closest analogy not in such sciences as 
ornithology or bryology—the science of 
birds or the science of mosses—but in such 
sciences as breeding, gardening or agri- 
culture. Possibly bee-keeping (apiculture) 
offers an analogy as useful as any. In api- 
culture bees are dealt with not so much as 
individuals, as communities or ‘ colonies,’ 
and the swarms are bred, cared for or cul- 
tivated largely as masses and by methods 
highly peculiar. Bacteriology is a kind of 
microscopic horticulture or apiculture, and 
its methods, introduced in the first instance 
by Pasteur for yeasts and twenty years later 
vastly improved by Koch, are applicable to 
many bacteria and yeasts—though certainly 
not equally to all—and also to some molds 
and other fungi, and, to some extent, to 
certain algze and protozoa. If we define 
as micro-organisms or microbes all organ- 
isms invisible or barely visible to the naked 
eye, we may conveniently describe their 
study as micro-biology. Bacteriology then 
is a sub-division of micro-biology and is con- 
veniently defined as the science of the cultur- 
able micro-organisms. 
Enough has perhaps been said already, 
in dealing with the origin of bacteriology, 
to indicate sufficiently the scope and sig- 
nificance of the culturable micro-organisms 
in nature. But when we reflect upon the 
simple fact that without their activity the 
habitable world and the sea would become 
SCIENCE. 
127 
one vast charnel-house, because there 
would be no adequate agency for mineral- 
izing dead matter, we begin to realize the 
enormous importance of the part which 
they play in the economy of nature. We 
have only to think of their helpful and 
wholesome unseen activity in removing 
from our view the dead animal bodies 
which would otherwise cover the earth, the 
dead leafage of the autumn, the worn-out 
trunks of trees, and the waste matters of 
human and animal life, in order to appre- 
ciate in some measure their fundamental 
importance in nature. When to this we 
and their tendency to cause the destruction 
of valuable organic matters, such as food 
and timber; their function in producing 
those fermentations, putrefactions and pois- 
onings of the human body which we know 
as epidemics, plagues, pestilences, infec- 
tious diseases, suppurating wounds, gan- 
grene and the like; when, furthermore, we 
consider their causative participation in 
such universal, familiar and important 
processes as bread-making, brewing, vine- 
gar-making, the fermentations of milk and 
its products, butter-making, cheese-making, 
lactic acid manufacture, tanning and nitri- 
fication, we are in a position to understand 
something of the scope and significance of 
the culturable micro-organisms, and there- 
fore of bacteriology, from a practical point 
of view. And while we cannot forget that 
our science had its most fruitful beginnings 
in pure science at the hands of a physiolo- 
gist, Schwann, and a natural philosopher, 
Pasteur, we must allow that its highest 
cultivation and its richest fruits have come 
from the labors of medical men. The 
names of Lister, Burdon-Sanderson, Koch, 
Behring, Roux and many others are the 
most famous, and their wonderful re- 
searches, with the brilliant practical re- 
sults of their labors for human welfare 
and progress, by far the most splendid 
achievements of bacteriology in the last 
