CULTTJRAL REQUIREMENTS OF BACTERIA 329 



with. It was, therefore, assumed as a working hypothesis, that 

 one or more amino acids were involved in the reactivation and 

 further efforts have been directed along the line of the isolation 

 of such compounds. 



Preliminary observations on distribution of activating material 



If only a single substance were concerned in the reactivation, 

 and it were one of the known amino acids, it should be possible 

 to gain a clue as to its nature by using the hydrolysates of sev- 

 eral different types of protein, and checking up a possible failure 

 to reactivate in certain cases against a common deficiency, a 

 method which has been widely used in work on animal metab- 

 oUsm. A number of proteins were, therefore, submitted to 

 sulphuric acid hydrolysis, and tested with decolorized infusion. 

 It appeared that the hydrolysates of casein, meat protein, edes- 

 tin, egg white, and to a lesser extent, egg yolk and gelatine, were 

 able to reactivate, while the material from wool, silk, and wheat 

 gluten were inactive. No common deficiency was apparent, 

 and the results in some cases were not always clear cut. Since 

 it will shortly be shown that two substances are probably involved 

 in the reactivation, it is quite possible that certain proteins may 

 lack one and not the other, and it wiU be necessary to run through 

 such a series of proteins again, testing for each substance indi- 

 vidually, when the properties of the two have been more carefully 

 investigated. 



Separation of an active fraction from casein hydrolysates with 

 mercuric sulphate 



After trying a number of methods for the separation of an 

 active fraction from hydrolyzed casein, with Uttle success, it was 

 finally found that a solution of mercuric sulphate in 5 per cent 

 sulphuric acid would serve to throw down a precipitate contain- 

 ing most, if not all, of the activating material. This separation 

 was first carried out upon a fraction containing the mono-amino 

 acids of casein prepared by the butyl alcohol extraction method of 

 Dakin (1918) which had been shown in preUminary experiments 



