F.ECES PLATING MEDIA. 25 



the surface of an agar slant. It is advisable to incubate overnight as a 

 test for sterility. 



BILE MEDIA. 



Secure ox bile from the abattoir or human bile from cases of gall- 

 bladder drainage in hospitals. Put about 10 c.c. in each tube and 

 sterilize. Some prefer to add i% of peptone. 



This is the medium for blood cultures in typhoid, etc. 



PLATING MEDIA FOR RECES WORK. 



The media of Endo, Conradi-Drigalski and the lactose litmus agar 

 medium are probably the most satisfactory of the numerous ones that 

 have been proposed for plating out faeces. A convenient way of pre- 

 paring any one or all of these, and which apparently gives media equal 

 to that prepared according to the original formulae, is as follows: 



Liebig's extract, 5 grams. 



Salt, 5 grams. 



Peptone, 10 grams. 



Lactose (C. P.), 10 grams. 



Agar, 20 grams. 



Water to make, 1000 c.c. 



Prepare as for ordinary nutrient agar, with the difference that 

 the reaction should be brought down to .5. 



For Endows Medium. Keep this lactose agar base in 100 c.c. 

 quantities in Erlenmeyer flasks instead of test-tubes. 



When needed for plating, melt a flask of this agar, and while liquid 

 add to the 100 c.c. ten drops of a saturated alcoholic solution of basic 

 fuchsin, and then twenty drops of a freshly prepared 20% solution of 

 sodium sulphite. The medium should be of a light flesh or pale 

 salmon color. 



Colon bacilli show on this medium as vermilion colonies, which in 

 about 48 hours have a metallic scum on them. Typhoid and dysentery 

 colonies are grayish. 



For Lactose Litmus Agar. Color the lactose agar base with 

 tincture of litmus to a lilac color. This may be tubed, putting 10 c.c. 



