4. Filter through papier Chardin. 5. Tube, and sterilise as for nutrient bouillon. ~Wheat Bouillon (Gasperini).~-- 1. Weigh out and mix wheat flour, 150 grammes; magnesium sulphate, 0.5 gramme; potassium nitrate, 1 gramme; glucose, 15 grammes. 2. Dissolve the mixture in 1000 c.c. of water heated to 100°C. 3. Filter through papier Chardin. 4. Tube, and sterilise as for nutrient bouillon. ~Bread Paste.~-- 1. Grate stale bread finely on a bread-grater. 2. Distribute the crumbs in sterile Erlenmeyer flasks, sufficient to form a layer about one centimetre thick over the bottom of each. 3. Add as much distilled water as the crumbs will soak up, but not enough to cover the bread. 4. Plug the flasks and sterilise in the steamer at 100° C. for thirty minutes on each of _four_ consecutive days. _Media for the Study of Parasitic Moulds._ ~French Proof Agar (Sabouraud).~-- 1. Weigh out Chassaing's peptone, 10 grammes, and emulsify it with 200 c.c. distilled water previously heated to 60°C. 2. Weigh out powdered agar, 13 grammes, and emulsify with 200 c.c. cold distilled water. 3. Mix the two emulsions and wash into a tared 2-litre flask with 600 c.c. distilled water. 4. Bubble live steam through the mixture for twenty minutes, to dissolve the agar. 5. Cool to 60° C. and clarify with egg as for nutrient agar (_vide_ page 168). 6. Filter through Papier Chardin, using the hot-water funnel. 7. Weigh out _French_ maltose, 40 grammes, and dissolve in the agar. 8. Tube, and sterilise as for nutrient agar. ~English Proof Agar (Blaxall).~--Substitute Witté's peptone for that of Chassaing, and proceed as for French proof agar. ~French Mannite Agar, Sabouraud.~--(_For cultivation of Favus._) Proceed exactly as in preparing French Proof agar _vide supra_ substituting Mannite (38 grammes) for maltose. _Media for the Study of Milk Bacteria._ ~Gelatine Agar.~--This medium is prepared by adding to nutrient gelatine sufficient agar to ensure the solidity of the medium when incubated at temperatures above 22° C. If it is intended to employ an incubating temperature of 30°C., 10 per cent. gelatine and 0.5 per cent. agar must be dissolved in the meat extract before the addition of the peptone and salt; while for incubating at 37°C., 12 per cent. gelatine and 0.75 per cent. agar must be used. Avoid the addition of more agar than is absolutely necessary, otherwise the action upon the medium of such organisms as elaborate a liquefying ferment may be retarded or completely absent. 1. Measure out 400 c.c. double strength meat extract into a "tared" 2-litre flask, and add to it gelatine, 100 grammes. 2. Weigh out powdered agar, 5 grammes, emulsify with 100 c.c., cold distilled water and add to the contents of the flask. 3. Dissolve the agar and gelatine by bubbling live steam through the flask for twenty minutes.