SPECIAL MEDIA 127 



3. Tube in the usual manner, and place in the Koch 

 inspissator (Fig. 37) two or three rows deep. 



4. Incline the inspissator to the proper angle, so as to 

 produce a large sloping surface of the serum. 



5. See that the water-jacket contains sufficient water. 

 Place a Bunsen burner below, slowly heat the water to the 

 boiling-point, and boil for 5 minutes. Then turn out the gas. 



6. Repeat this process upon the two following days at 

 the same hour. 



NOTE. Always place about 25 c.c. of water in the inspissator 

 along with the tubes, so as to keep up a saturation of the air in 

 the apparatus. By doing this, one avoids giving the serum a dry 

 surface. See that the inspissator contains a rack made of wooden 

 or metal strips, which keeps the tubes from touching the bottom 

 and wall ; otherwise the serum will be overheated forming bubbles 

 in the mass. 



Litmus -solution. Dissolve i part of Merck's pure extract 

 of litmus in 100 parts of water, filter through paper, and steri- 

 lize. 



Glycerin-broth. Add 6 per cent, of pure glycerin to 

 ordinary broth. 



Glucose-gelatin. Add i per cent, glucose to ordinary 

 gelatin. 



Litmus-lactose-agar (for plating). Add i per cent, of 

 lactose to sugar-free agar, distribute 8 c.c. in culture-tubes, and 

 add i c.c. of sterile litmus-solution to each tube before using. 



Litmus -lactose- gelatin (for plating}. Prepare gelatin in 

 the usual manner, using 10-12 per cent, of gelatin, and dis- 

 solve i per cent, of lactose. Distribute 8 c.c. into culture- 

 tubes, and add litmus-solution to each tube before using. 



NOTE If i c.c. of the liquid to be analyzed is added, 14$ 

 of gelatin should be used. 



Litmus -mannit-agar . Prepare like litmus-lactose-agar, 

 substituting i per cent, mannit in place of lactose. 



Neutral-red agar. Add enough 0.5 per cent, neutral-red 



