148 Annual Report of the Royal Veterinary College on 
When the steriliser is prepared for use, the tubes, flasks, or instruments 
are placed in a suitable vessel and lowered into the steam chamber ; a 
Bunsen burner is applied underneath, and in a few minutes steam rises, and 
can be maintained as long as may be required ; the water which has evaporated 
being automatically replaced from the reservoir through the connecting tube (6). 
When the contents of a flask or tube have by this means been made pure or 
sterile, they can be kept so by simply plugging the orifice with cotton wool, 
which is found to act as a filter to the air which may pass through it. 
In practice it is found that micro-organisms may be cultivated upon 
various media, such as the cut surface of a potato, a slice of beetroot, bread 
paste, and blood serum ; but by far the most useful medium is the peptouised 
extract of beef and gelatine, so well known to all workers in this branch of 
scientific investigation. It is now usually made 
in considerable quantities, and kept ready for use 
in large flasks, an ingenious arrangement of which 
(shown in fig. 2) enables it to be drawn oft' into 
small tubes. 
This is also the method of obtaining deposits 
from milk. The cream, rising to the top, leaves 
any sediment in the neck of the inverted flask, 
from which it may be easily withdrawn by means 
of the tap. Urinary deposits may be obtained in 
the same way. 
Many of these organisms or germs reqxure a 
higher temperature than that of our atmosphere 
for their cultivation, and when an investigation is 
being made into their action and efiects on the 
tissues of an animal, it is needful to cultivate them 
at the same temperature as the animal's body. 
For this purpose incubators are employed very much after the fashion of the 
"Artificial Mother" so well known to all interested in jioultrv, the source 
of heat being regulated automatically. The incubators in this case, how- 
ever, are specially fitted up to receive tubes, flasks, and plates instead of 
eggs and chickens. 
During an investigation into the cause of an outbreak of disease among 
cattle it may be found requisite to grow hundreds of these minute fungi in 
test-tubes and upon all of the media already mentioned, before the particular 
one which has caused the mischief can be discovered. Even when this stage 
has been reached we are only iipon the threshold of our investigation, for 
it must be further determined now this organism jn-opagates itself, uhder 
which of many conditions does it best thrive ; its variations of form under 
each of those conditions must be registered, so that in future outbreaks it 
may be more easily recognised. After all this lias been accomplished it still 
remains to be investigated how this disease-producing germ has obtained an 
entrance into the animal, how it caused the lesions which may be di.'^covered 
in the various parts of the carcass, and, again, tlv! nalcod-eyo and tlie micro- 
scopical appearance of th(>se parts must be fully and accurately described. 
It is proved beyond doubt by many failures that we must not rest content 
witlx doing all this once only; again and again has the whole procedure to 
be pone through, and vari^'d so tliat errors of judgment and of manipulation 
may be elimiuated before the result can be nuule public. 
When it is necessary to examine the diseased carcass, a post-mortem 
examination is made, and, as has been already stated, the Tiaked-eye 
appearance, size, and weight of the various organs are placed on record ; 
then portions of these organs are prep ired for a further examinatiou under 
the microscope by being hardened in " Muller's fluid " or in alcohol. If the 
