14 MICRO-ORGANISMS IN WATER 



the gelatine, but if the original acidity of the wort 

 is required the excess must be carefully neutralised 

 by means of sodium phosphate. For wort agar the 

 mode of preparation is quite similar, excepting that 

 1 to 2 per cent, of agar is substituted for the gelatine. 

 Under the examination of water for brewing purposes 

 (see p. 67) an account will be found of the various 

 culture fluids used by Hansen and his pupils for this 

 purpose. 



Miquefs high-temperature jelly. The discovery was 

 made by Globig of some organisms which apparently 

 would not grow at a temperature below 50 C., and 

 Miquel has devised a culture medium which will re- 

 main solid at this high temperature. For this pur- 

 pose from 300 to 400 grams of Irish moss (Caragheen, 

 Fucus crispus) are placed in 10 litres of water and 

 heated for several hours at 100 C. ; the liquid is then 

 poured through a sieve, the filtrate boiled up again, 

 and strained whilst hot through fine linen. The filtrate 

 is slowly evaporated on a water-bath, and is then 

 placed in porcelain dishes and dried at from 40 to 

 45 C. Miquel states that 1 per cent, of the gelatinous 

 substance thus obtained on being added to broth yields 

 a culture material remaining solid at 50 C. 



Iron gelatine and iron agar. In order to deter- 

 mine the production of sulphuretted hydrogen by 

 certain bacteria, Fromme l prepared a culture material 

 consisting of gelatine peptone, to which a small 

 quantity of iron (the exact quantity is not specified) 

 was added. The iron is added in the form of a 3 per 

 cent, solution of ferrous tartrate, acetate, or saccharate 

 to the gelatine, and the material assumes a faint reddish 

 colour. Fromme cultivated various pathogenic organisms 



1 Ueber die BezieTiung des metallischen Eisens zu den Bakterien. 

 Marburg, 1891. 



