58 APPLIED BACTERIOLOGY 



anaerobic bacteria. The tubes for this purpose are filled 

 two-thirds full. . 



(11) TJrine Gelatine and Agar. — Fresh urine thickened 

 with 10 per cent, of gelatine, or 2 per cent, of agar, with 

 the addition of 1 per cent, of peptone and J per cent, of 

 sodium chloride, is rendered feebly alkaline and filtered. 

 The details of the method of preparation are the same as 

 those already described for nutrient agar and gelatine. 

 These two media are largely used in Germany, and are 

 said to yield equally satisfactory results to those prepared 

 from broth. 



(12) Peptone Solution. — Ten grammes of peptone and five 

 grammes of sodium chloride are dissolved in 1,000 c.c. of 

 distilled water ; the solution is then well boiled, and neutra- 

 lised carefully in the usual manner. The solution is again 

 boiled and filtered. The solution is then run into tubes, 

 and steamed for fifteen minutes on three successive days. 

 These tubes are used in the diagnosis for cholera. 



(13) Milk-tubes.—' Separated ' milk is carefully neutra- 

 lised with sodium bicarbonate and filled into tubes, and 

 sterilised as usual. These tubes' are useful for the differ- 

 entiation between typhoid and coli. 



(14) Potato-tubes.— Large and sound potatoes are tho- 

 roughly scrubbed until clean, and then with a large cork- 

 borer cylindrical pieces are bored to fit into test-tubes. 

 Each cylinder is cut into two halves diagonally, and each 

 half placed in a test-tube. It is advisable to allow the 

 cores of potato to rest on a moist plug of cotton-wool ; this 

 will keep the potato-cylinder moist. The tubes are then 

 plugged and capped as usual, and sterilised for thirty 

 minutes in the steam steriliser on three successive days. 



Potatoes form an excellent culture medium for many 

 organisms, and one which secures their development in a 

 very characteristic way. Care should be taken to prevent 



