Vol. IL, No. 2, MARCH, 1884.] 
BACTERIA.* 
a 
A handful of hay infused in hot water produces a brown 
fluid closely resembling tea, and, if strained through muslin or 
blotting paper, perfectly clear and limpid. Ifa drop of this “ay 
infuston be examined under the microscope, it is found to be free 
from life—indistinguishable indeed from a drop of pure water. 
But if a glassful of the fluid be set aside, it is found speedily to 
alter its character. Ina few days—two or three in summer, 
longer in winter—it becomes slightly turbid ; soon the turbidity 
increases and a scum forms on the surface ; the scum thickens, 
breaks up, and fall in shreds to the bottom, and the fluid gradu- 
ally becomes clear once more. 
Any other infusion of either animal or vegetable matter—tea, 
cabbage-water, mutton-broth, the water in which fish has been 
boiled—will be found to undergo similar changes ; turbidity al- 
ways ensues in a short time, then a scum forms on the surface, 
and finally, after a longer or shorter interval, the fluid clears again. 
But for purposes of study, hay-infusion has one great advan- 
tage,—during the whole series of changes, the smell arising 
from it is very slight, whereas in the case of all animal and many 
vegetable infusions, the whole period of turbidity is distinguished 
by a horrible odour of putrefaction. The appearances I have 
described in the hay-water are, in fact, the normal optical effects 
of putrefaction in an organic fluid. 
Suppose now that a drop of turbid hay-infusion is examined 
under the microscope—one magnifying 400 or 500 diameters is 
necessary. The sight is enough to form an epoch in the life of 
anyone seeing it for the first time, and indeed even a hardened 
microscopist can scarcely behold it without renewed wonder. 
In the small space—a circle of about one-fiftieth of an inch 
in diameter—forming the “field” of the microscope, one sees 
thousands of tiny specks rushing about in all directions, knock- 
ing against one another, tumbling over and over, and altogether 
performing the maddest dance imaginable. These specks are 
Bacteria. 
Let us now concentrate our attention on a single Bacterium, 
and find out something of its characters. Each consists of a 
simple spindle-shaped body, or of two spindles placed end to end, 
and is formed of a tolerably firm semi-transparent substance. It 
has been found by careful measurement that the entire length of 
one of these little double spindles is one ten-thousandth of an 
inch, and its breadth one twenty-thousandth of an inch, which 
*A lecture delivered at the Oamaru Athenzum and Mechanics Institute, on 
30th January, 1884, by Prof. T. Jeffery Parker, ; 
