1. Prepare blood-serum as described, page 168, sections 1 to 4. 2. Add 5 per cent. pure glycerine. 3. Complete as described above for ordinary blood-serum, sections 5 to 7. NOTE.--Different percentages of glycerine--from 4 per cent. to 8 per cent.--are used for special purposes. Five per cent. is that usually employed. ~Blood-serum (Loeffler).~-- 1. Prepare nutrient bouillon (_vide_ page 163), using meat extract made from veal instead of beef. 2. Add 1 per cent. glucose to the bouillon, and allow it to dissolve completely. 3. Now add 300 c.c. clear blood-serum (_vide_ page 168, sections 1 to 4) to every 100 c.c. of this bouillon. 4. Fill into sterile tubes and complete as for ordinary blood-serum. ~Blood-serum (Lorrain Smith).~-- 1. Collect blood-serum (_vide_ page 168, sections 1 to 4), as free from hæmoglobin as possible. 2. Weigh out 0.15 per cent. sodium hydrate and dissolve it in the fluid (or add 0.375 c.c. of dekanormal soda solution for every 100 c.c. of serum). 3. Tube, and stiffen at 100° C. in the serum inspissator. 4. Incubate at 37° C. for forty-eight hours to eliminate any contaminated tubes. Store the remainder for future use. ~Blood Serum (Councilman and Mallory).~-- 1. Collect blood serum in slaughterhouse, coagulate, remove serum and tube (_vide_ page 168). Great care must be taken to avoid the inclusion of air bubbles--indeed if only a few tubes are filled at one time, it is a good plan to stand them upright in the receiver of an air pump and to exhaust as completely as possible before transferring to the serum inspissator. 2. Heat the tubes in a slanting position in hot-air steriliser at 90° C. till firmly coagulated, say half an hour. 3. Sterilise in steam steriliser at 100° C. for 20 minutes on each of three successive days. Resulting medium not translucent, but opaque and firm. _B. Tuberculosis._ ~Egg Medium (Lubenau).~-- This modification of Dorset's egg medium (_quod vide_ page 174) is preferred by some for the growth of the tubercle bacillus of the human type. It consists in the addition of one part of 6 per cent. glycerine in normal saline solution, to the egg mixture between steps 4 and 5. ~Glycerine Bouillon.~-- 1. Measure out nutrient bouillon, 1000 c.c. (_vide_ page 163, sections 1 to 6). 2. Measure out glycerine, 60 c.c. (= 6 per cent.), and add to the bouillon. 3. Tube, and sterilise as for bouillon. ~Glycerine Agar.~-- 1. Prepare nutrient agar (_vide_ page 167, sections 1 to 8). Measure out 1000 c.c. 2. Measure out pure glycerine, 60 c.c. (= 6 per cent.), and add to the agar. 3. Tube, and sterilise as for nutrient agar. ~Glycerine Blood-serum.~-- 1. Prepare blood-serum as described, page 168, sections 1 to 4. 2. Add 5 per cent. pure glycerine. 3. Complete as described above for ordinary blood-serum, sections 5 to 7.