300 ON THE GERM THEORY OF PUTREFACTION 
glass slip above that. This slip is also useful in the stocking of the glass garden. 
Having been taken up from the other glasses, it is placed inverted on the table, 
so that the surface which was downwards during the cooling, and therefore 
free from dust, may be directed upwards. A few drops of the new liquid 
medium, in which development is intended to occur, are then placed upon it 
with ‘heated’ pipette, and to these a minute portion of the organism is added 
and diffused thoroughly among the fluid by stirring with a ‘ heated’ glass rod. 
The thin covering glass being now raised by means of ‘ heated’ forceps, aided 
in the manipulations by a ‘ heated’ needle, a very small drop of the mixture of 
organism and medium is placed, by means of the pipette, upon the central 
island of the garden, and, in order to ensure a moist atmosphere in the air- 
chamber, a drop of water, which has been boiled, and cooled under protection 
from dust, is introduced with a clean ‘ heated’ pipette into the ditch... The thin 
covering glass, which has been still held in the purified forceps, is then accurately 
replaced, after which its margins are luted down with paraffin, which is con- 
veniently melted in an egg-spoon, and applied with a clean steel pen heated 
from time to time in the spirit-lamp. This process requires considerable delicacy 
and quickness of manipulation, and constant watchfulness; but with these 
conditions it may be conducted with most satisfactory results; and I have 
watched one and the same organism continuing to grow unmixed in such a 
garden for several weeks together, though carried about with me in a journey 
made in an autumn holiday. 
As soon as the stocking of the garden is completed, it is placed under the 
microscope, and some individual specimens of the organism are sketched by 
camera lucida—a map, on a smaller scale, being also made with the camera to 
enable the observer to find the objects again. 
On the 11th of September I stocked such a garden with a little of the scum 
from the second urine-glass, mixed with uncontaminated urine from one of the 
glasses charged on the roth of August, the liquid still retaining its original bright- 
ness and fresh odour. The cells of the scum thus introduced between the island 
and the covering glass were all of the spherical character, as is illustrated by 
the groups at a in Plate X, sketched at 7.20 p.m., within a few minutes of their 
* The actual order of proceeding is to introduce the boiled water into the air-chamber first, after 
which the same pipette, being clean, may be at once used for the liquid medium. I have found the 
most convenient form of pipette for these experiments to be a small syringe, having its nozzle connected, 
by means of a short piece of caoutchouc tubing, with a glass tube very narrow and thin, so that it is 
almost instantaneously heated nearly to redness by passing it through a flame, and cools with corre- 
sponding rapidity. The tube is bent near its middle at about a right angle ; so that neither the syringe 
nor the hand is held over the experimental glass, while the yielding nature of the caoutchouc junction 
allows the end of the glass tube to be pressed, without risk of breaking, against any object, such as the 
side of a wine-glass, from which an organism is being picked up. 
