the hot agar.

3. Tube, and sterilise as for nutrient agar.

NOTE.--The Sulphindigotate media are of a blue colour, which
during the growth of anaerobic bacteria is oxidised and
decolourised to a light yellow.

FOOTNOTES:

[4] This figure is obtained by adding together 1 litre water, 1000
grammes; 10 per cent. gelatine, 100 grammes; 1 per cent. peptone, 10
grammes; 0.5 per cent. salt, 5 grammes; total, 1115 grammes.
Modifications of the above process, as to quantities and percentages,
will require corresponding alterations of the figures. The average
weight of a measured litre of 10 per cent. nutrient gelatine when
prepared in this way _after filtration_ is 1080 grammes.

[5] This figure is obtained by adding together 1 litre of water (meat
extract), 1000 grammes; 2 per cent. agar, 20 grammes; 1 per cent.
peptone, 10 grammes; 0.5 per cent. salt, 5 grammes--total 1035 grammes.
Modifications of the process as to quantities or percentages will
necessitate corresponding alterations in the calculated medium figure.
The average weight of a measured litre of 2 per cent. agar when prepared
in this way, _after filtration_, is 1010.5 grammes.

[6] "Hopped" wort exerts a toxic effect upon many bacteria, including
the lactic acid bacteria.

XII. SPECIAL MEDIA.

In this chapter are collected a number of media which have been
elaborated by various workers for special purposes, grouped together
under headings which indicate their chief utility. In many instances the
name of the originator of the medium is given, but without reference to
his original instructions, since these are in many cases inadequate to
the requirements of the isolated worker, who would probably fail to
reproduce the medium in a form giving the results attributed to it by
its author. Such modifications have therefore been introduced as make
for uniformity between the different batches of media.

A considerable number of coloured media, chiefly intended for work with
intestinal bacteria, have been included; but beyond the fact that the
author's modification of the Drigalski-Conradi medium has been included
amongst the routine media of the laboratory, no comment has been made
upon their relative values, since only by observation and practice can
the skill necessary to utilise their full value be acquired.

The instructions as to sterilisation are rarely given in full; the
routine method of exposure in the steam steriliser at