USCHINSKY'S MEDIUM. 495 



organism can produce gas and a diffused growth. The 

 latter is an excellent indication of the presence of motion. 

 The Hiss medium can be modified by substituting^ 3U 

 per cent, of lactose for the glucose, and by rendering the 

 medium alkaline and then adding litmus. The medium thus 

 modified will indicate acid and gas production as well as 

 diffusion. 



Uschinsky's Medium. 



As seen from the formula, this is an artificial medium 

 made up of simple chemical compounds and wholly free 

 from protein matter. The organisms planted on this medium 

 are therefore obliged to build up their protoplasm from 

 simple organic and inorganic bodies. The medium has been 

 of great value in the. study of the products produced by the 

 bacterial cell. It possesses the following composition: 



Water, 1000 parts, Magnesium sulphate, 0.2 0.4 part, 



Glycerin, 30-40 parts, Di-potassium phosphate, 2-2.5 parts, 



Sodium chloride, 5-7 parts, Ammonium lactate, 6-7 parts, 



Calcium chloride, 0.1 part, Sodium asparaginate, 3-4 parts. 



On the medium prepared as above, contrary to Uschin- 

 sky, the typhoid (and Sanarelli) bacillus will not grow, 

 whereas the colon bacillus yields an excellent growth: The 

 medium, therefore, can be used to good advantage in differ- 

 entiating between these organisms. 



Fraenkel has simplified the above solution by elimina- 

 ting those constituents which are not necessary for the 

 growth of bacteria. This modified solution contains 5 g. of 

 NaCl, 2 g. of potassium di-phosphate, 6 g. of ammonium 

 lactate and 4 g. of sodium asparaginate. Asparagin may 

 be substituted for the latter and the neutral phosphate of 

 sodium, for the phosphate of potassium, whereas the sodium 

 chloride may be omitted. Fraenkel observed that in this 

 medium the Eberth bacillus scarcely developed, whereas 

 the colon bacillus gave a rapid, strong growth. 



