1901 - 2 .] Plague Research Laboratory of Government of India. 119 
and oblately spheroidal in shape. Two litres of fluid in these flasks 
form a layer of barely two inches thick, thus affording a very 
large surface for aeration of the growing bacilli. 
This medium has been found excellent for the growth of all 
sorts of bacteria, and has proved much cheaper than the ordinary 
method of making meat extract, and then adding commercial 
peptone, for not only is the expense of buying peptone avoided 
— and we used to use as much as twenty-five shillings’ worth in 
a day — but from one kilo of meat we make as much as 9 or 
10 litres of bouillon, as against 2 by the old method. This 
medium is known in the laboratory as ‘ Warden’s bouillon,’ but 
the process of gradual digestion in the water bath and treating 
with charcoal are modifications devised by Dr F. Maitland 
Gibson, one of the permanent staff. A similar bouillon was also 
made by the latter official having for its basis wheat flour, from 
which the starch has been removed by washing, but it is not 
at present widely used. It was made to meet the objections 
of some vegetarian sections of the native community, and though 
not now much in demand, has served the purpose of reconciling 
some of the leading native practitioners to the use of the 
prophylactic. 
Into each flask thus made ready for final sterilising are dropped 
four drops of cocoanut oil, whicli produces an abundance of droplets 
on the surface, without forming a continuous layer of oil on the 
bouillon. The necks of the flasks are plugged with sterilised cotton 
wool in the ordinary way, and the whole batch of fifty or sixty 
sent out to the corrugated iron shed containing the big steriliser 
(fig. 3). This steriliser is merely a jacketed clothes disinfector 
made strong enough to stand a pressure of 15 lbs. to the square 
inch, and with a trolly fitted with shelves on which sixty flasks can 
be safely placed. The flasks are kept under this pressure for one 
and a half hours, one hour having in practice been found insufficient 
to sterilise their contents when working on this wholesale scale. 
The flasks containing the sterilised bouillon with the layer of oil 
on the surface are now taken to the incubation room to be sown 
with plague bacilli. It is therefore necessary to explain where 
the germs come from and how a pure culture of them is produced. 
It is unfortunately easy at any time of the year to find cases of 
