CULTURE MEDIA. 4” 
as carbolic acid, etc., have also been used for the same purpose, and 
it has been shown by experiment that some bacteria will grow in a 
medium containing such agents in a proportion which would entirely 
restrain the development of others. 
The soluble silicates which form a jelly-like mass have been 
proposed as a culture medium for certain bacteria which do not grow 
in the usual media. Kiihne (1890), Winogradsky (1891), and Sles- 
kin (181) have made experiments which indicate that this medium 
has considerable value. 
Winogradsky uses in the preparation of his silicate jelly the 
following salts : 
Ammonium sulphate, : : ; 0.4 gramme 
Magnesium sulphate, . 0.05 s 
Potassium phosphate, : 4 : 0.1 ~ 
Calcium chloride, : : ; a trace. 
Sodium carbonate, ‘ ; 0.6 to 0.9 gramme. 
Distilled water, : P : e 4 100 grammes. 
To this he adds a solution of silicic acid. According to Kiihne, a 
solution containing 3.4 per cent of silicic acid and having a specific 
gravity of 1.02 may be preserved in a liquid condition. To this the 
salts are added in greater or less amount, according to the consis- 
tence desired. 
Sleskin states that a suitable jelly is formed by the addition of 
1.15 to 1.45 per cent of the salts, and recommends that concentrated, 
sterilized solutions be added to the acid. He dissolves separately, in 
as little water as possible, the sulphates, the potassium phosphate 
and sodium carbonate, and the calcium chloride. 
The use of a culture medium containing an extract from the je- 
quirity seeds has been recommended by Kaufmann (1891), who has 
found, by experimenting upon various bacteria, that such a medium 
is useful in differentiating species. 
The jequirity solution, which may be used as a liquid medium 
or may be employed in the preparation of nutrient gelatin or agar, is 
prepared as follows: Ten grammes of jequirity seeds are bruised in 
a mortar and the shells removed ; they are then placed in one hun- 
dred cubic centimetres of water and cooked for two hours in the steam 
sterilizer ; after allowing the infusion to cool it is filtered. The fil- 
tered liquid has a pale-yellow color and a neutral or slightly alkaline 
reaction. Certain bacteria grow in this solution without producing 
any change in its color; others, which produce an acid reaction, 
cause it to be decolorized ; others, which produce an alkaline reac- 
tion of the medium, change the color to green. 
Lactose Litmus-Agar.—This medium is useful for the detection 
of the typhoid bacillus in mixed cultures, e.g., in feces. It is made 
by adding to nutrient agar-agar, having a slightly alkaline reaction, 
