MEAT EXTRACT BOUILLON 37 



or feebly alkaline reaction. Turbidities are either caused 

 by the reaction being strongly alkaline, and are in that case 

 removed when this is corrected, or are due to a finely fioccu- 

 lent precipitate of albuminates, which are cleared away by 

 adding the white of a hen's egg and boiling for a quarter of 

 ah hour [with subsequent filtration]. 



Preparation of meat extract bouillon. — A second mode of 

 making bouillon consists in the combination of meat-extract 

 and sugar to obtain a liquid culture medium. The fol- 

 lowing is Hueppe's process : — To a litre of water are 

 added ^ per cent (5 grams) of extract of meat and 3 per 

 cent. (30 grams) of dry peptone, or instead of extract of 

 meat and peptone, 2 to 8 per cent. (20-30 grams) of 

 peptone of meat. A further addition of five grams of grape 

 or raw sugar is then made, and the liquid boiled, carefully 

 neutrahsed with solution of sodium carbonate, and subse- 

 quently sterilised. Admixture of glycerine with the bouillon 

 is also advantageous, and tubercle bacilli grow excellently 

 on the medium thus obtained. 



Solutions of white of egg. — Solutions of white of egg are 

 well suited to form fluid culture-media after they have 

 been completely freed from germs by the discontinuous 

 method of sterilisation. The white of plovers' eggs lends 

 itself well to this purpose, being clear and transparent, and 

 capable of dilution with water, and of being filtered ; it 

 admits also of the addition of dextrine, sugar, or other 

 ngredients according to need. The albumen when sterilised 

 affords for a considerable time a suitable medium for culti- 

 vations in test tubes or on glass plates placed in the 

 moist chamber. 



Solid nutrient media. — Owing to the introduction of the 

 use of solid culture media in bacteriological research, 

 a series of micro-organisms have been more thoroughly 

 examined, and it has thus been possible to observe that 



