118 Proceedings of Royal Society of Edinburgh. [sess. 
(158° F.), kept warm in a jacketed tub. The jars are left there 
for a week, by which time the meat has become dissolved so that 
the contents look like brown porridge. The albumen has become 
converted into acid albumen with a little albumose and peptone. 
The fluid is now transferred to large glazed earthenware jars, and 
water is added to make the bulk equal to three litres of fluid for 
each kilo of meat originally present. The large jars are now 
placed in the autoclaves, and kept there for three hours under a 
steam pressure of three atmospheres, or 44 T lbs. to the square inch, 
which gives a temperature of about 143° C. (290° F.). 
The fluid after this treatment is dark brown and somewhat 
viscid, containing quantities of undigested fibrous tissue, etc. It 
is undoubtedly rich in albumoses and peptones, but the amount 
of each has not yet been determined. This fluid is filtered and 
made up to the original bulk of three litres per kilo. Bone 
charcoal is now added in the proportion of 150 grammes per 
litre, and the whole well stirred for a quarter of an hour. This 
improves the colour of the bouillon and also its cultural properties. 
The charcoal is then roughly strained out by means of a cloth, 
and the fluid neutralised by the addition of caustic soda. It 
is also diluted by the addition of from two to two and a half 
volumes of water for each volume of peptone solution. In this 
dilution the amount of hydrochloric acid used, when neutralised as 
above, gives a bouillon containing 0*5 per cent, of chloride of sodium 
or common salt. If the bouillon is required for ordinary laboratory 
purposes, each volume of the peptone solution is diluted with from 
three to five volumes of water, and in this case more salt has to be 
added to get the 05 per cent, required for the nutriment of bacteria. 
This mixing and neutralising is done in a wooden tub holding 
about 60 litres, for it is quite a common thing for us to produce 
50 litres or more of bouillon daily. The neutralising is in the 
first place purposely carried too far, for during the heating process 
the reaction goes back, and a perfectly neutral fluid is necessary for 
the proper growth of the bacillus pestis. The fluid is then heated 
for an hour under a pressure of 15 lbs. to the square inch (121° C_ 
or 250° F.) to throw down the phosphates, etc., refiltered and distri- 
buted in quantites of 2 litres into 4-litre flasks. These flasks 
are specially made for us in Paris, of pale green glass, flat-bottomed 
