PREPARATION OF PEPTONES 2O5 



then it is similarly freed from water, as far as possible, 

 before being placed in sulphuric acid, which is kept 

 cool by means of ice. Nervous tissue, after it has 

 been deprived of all blood and boiled, must first be 

 extracted with carbon tetachioride, as otherwise its 

 lipoidal sheath makes decomposition very difficult. 

 Tubercle bacilli must also be freed from lipoids. 



For hydrolysis, we use 70 per cent, (by weight) of 

 sulphuric acid, which must be cold. We take three 

 times as much of this, as of the tissue to be decom- 

 posed. The vessel is energetically shaken, and then 

 carefully stoppered. From time to time it is shaken 

 again. The tissue is soon dissolved, the solution 

 becoming more or less brown. After standing for 

 exactly three days, at the temperature of the room 

 (20 C. at most), the vessel containing the hydroly- 

 sate is placed into iced water, and diluted with ten 

 times its quantity of distilled water. The addition 

 must be made very gradually. The temperature of 

 the solution is controlled bv means of a thermometer, 



J 



and must never be allowed to rise above 20 C. If 

 the vessel is too small, then the solution is trans- 

 ferred into a larger one, and the water with which 

 we are diluting is used to rinse the first vessel. 



We now begin the neutralization of the sul- 

 phuric acid with barium hydroxide. Pure crystalline 

 hydroxide is employed for this purpose, and this 

 is gradually added, until the solution gives no 



