and add to contents of flask. 4. Measure out 25 c.c. of the solution and titrate it against decinormal sodic hydrate, using litmus as the indicator. Control the result and estimate the amount of sodic hydrate necessary to be added to render the remainder of the solution neutral to litmus. Add this quantity of sodic hydrate. 5. Filter. 6. Add litmus solution 47.5 c.c. (= 5 per cent.). 7. Tube, and sterilise as for nutrient bouillon. ~Capaldi-Proskauer Medium No. II.~-- 1. Weigh out and mix Peptone 20 grammes Mannite 1 gramme 2. Dissolve in water 1000 c.c. in a 2-litre flask. 3. Neutralise to litmus as in No. I (_vide supra_, Step 4). 4. Filter. 5. Add litmus solution 47.5 c.c. (= 5 per cent.). 6. Tube, and sterilise as for nutrient bouillon. ~Urine Media. Bouillon.~-- 1. Collect freshly passed urine in sterile flask. 2. Place the flask in the steamer at 100° C. for thirty minutes. 3. Filter through two thicknesses of Swedish filter paper. 4. Tube, and sterilise as for nutrient bouillon. (Leave the reaction unaltered.) ~Urine Gelatine.~-- 1. Collect freshly passed urine in sterile flask. 2. Take the specific gravity, and, if above 1010, dilute with sterile water until that gravity is reached. 3. Estimate (with control) at the boiling-point, and note the reaction of the urine. 4. Weigh out gelatine, 10 per cent., and add to the urine in the flask. 5. Heat in the steamer at 100° C. for one hour to dissolve the gelatine. 6. Estimate the reaction and add sufficient caustic soda solution to restore the reaction of the medium mass to the equivalent of the original urine. 7. Cool to 60° C. and clarify with egg as for nutrient gelatine (_vide_ page 166). 8. Filter through papier Chardin. 9. Tube, and sterilise as for nutrient gelatine. ~Urine Gelatine (Heller).~-- 1. Collect freshly passed urine in sterile flask. 2. Filter through animal charcoal to remove part of the colouring matter. 3. Take the specific gravity, and if above 1010, dilute with sterile water till this gravity is reached. 4. Add Witté's peptone, 1 per cent.; salt, 0.5 per cent.; gelatine, 10 per cent. 5. Heat in the steamer at 100° C. for one hour, to dissolve the gelatine, etc. 6. Add normal caustic soda solution in successive small quantities, and test the reaction from time to time with litmus paper, until the fluid reacts faintly alkaline. 7. Cool to 60° C. and clarify with egg as for nutrient gelatine (_vide_ page 166). 8. Filter through papier Chardin. 9. Tube, and sterilise as for nutrient gelatine. ~Urine Agar.~-- 1. Collect freshly passed urine in sterile flask. 2. Take the specific gravity and if above 1010, dilute with sterile water till this gravity is reached. 3. Weigh out 1.5 per cent. or 2 per cent. powdered agar, and add it to the urine. 4. Heat in the steamer at 100° C. for ninety minutes to dissolve the agar. 5. Cool to 60° C. and clarify with egg as for nutrient agar (_vide_ page 168).