46 MEDIA AND THEIR PREPARATION 
Breed (1915) has shown that by increasing the peptone content of 
nitrate broth to 5 gms. per liter more uniform results were obtained 
when fifty cultures of B. colt were tested for nitrate reduction. With 
soil bacteria 1 per cent peptone seemed to allow more constant results. 
He concludes that nitrate destruction must be tested for in media which 
allows a vigorous growth of the organisms. Suitable nitrate broths 
may have to be devised to fit each group. 
Neutral Red Broth (Houston, 1914). 
Peptone............. eee eee eee eee eee 10 gms. 
Salt, NaCl... 0... eee een 5 gms. 
Plain broth... 0.0... eee 1000 c.c. 
Add 2 ¢.c sterile aqueous 1 per cent solution of neutral red per liter. 
Make slightly alkaline with 20 per cent KOH. Tube and sterilize. 
Bile Salt Broth (MacConkey, 1900). 
Peptone... 02... eee cc eee 20 gms 
Desiccated bile.... 22.2... 2. eee ee eee 5 gms 
Dextrose (C6Hi206)... 2.6... ee eee 5 gms. 
Distilled water... 2.0.0.0... eee eee 1000 c.c. 
Boil for twenty minutes and add sterile litmus solution to color. 
Filter and put in fermentation tubes. 
Vegetable Bouillon (Berthelot, 1917). This medium may be used 
as a substitute for meat infusion and is prepared as follows: 
Water. ccc cece cee ee eee nes 4000 ¢.¢ 
Potato... ee cece te ete eens 300 gms 
Carrots... 0... cece cece nent ete 150 gms. 
TUIMIpS.. 2 ee cee eee eee eee 150 gms. 
Peel the potatoes and wash the carrots and turnips. Cut them into 
small pieces and put in cold water. Boil for four hours, strain and make 
feebly alkalin. Heat in an autoclave at 120° C. for one-half hour 
and allow to stand over night in a refrigerator. Filter through paper. 
Chicken Broth (Besson, 1913). Five hundred grams of lean chicken 
meat are soaked in water and filtered. The filtrate is used in the 
same manner as beef broth. 
Giblet Broth (Besson, 1913). Liver, spleen, etc., may be used for 
making broth. Five hundred grams of the solid organs are soaked 
and filtered. The filtrate is,used as in other media of this sort. 
