QUANTITATIVE DIGESTION EXPERIMENTS. 241 



sary, in order to recognize disturbing influences, to shorten 

 the duration of the digestion even to four hours. The 

 answer to the question whether a substance disturbs the 

 digestion cannot, therefore, strictly speaking, be given in 

 general, x but only applies for the special conditions adhered 

 to in the experiment. Of course there are also substances 

 which interfere with the digestion even when the conditions 

 for the digestion are the most favorable, e.g., larger quanti- 

 ties of sugar, gum, or plant-mucus. 1 When fibrin or coagu- 

 lated albumin, etc., is used we may either determine the 

 undissolved albumin or the dissolved or both. When an 

 albumin solution is used the determination of that which 

 remains undissolved is of course omitted. If we limit our- 

 selves to the determination of the portion remaining undis- 

 solved, then the precipitate formed on neutralization would 

 be included among the products of the digestion, which is 

 scarcely justifiable. At all events, it is preferable to deter- 

 mine the undissolved albumin + the precipitable albumin 

 on the one hand and the peptonized (album ose and peptone) 

 on the other, or to determine the quantity of the albumin 

 present at the beginning of the digestion and the quantity 

 of the peptonized material in the mixture of digestion prod- 

 ucts. 2 It is advisable to replace the very long and also not 

 quite accurate determination of the dry residue by the 

 Kjeldahl nitrogen determination. One example of this kind 

 of experiment may suffice. 



Blood -serum is treated with an equal amount of water, 

 shaken thoroughly, and exactly neutralized with dilute 

 hydrochloric acid. 



1 Mugdan, Berl. klin. Wochenschr., 1891, No. 32. 



2 If we also estimate at the same time the quantity of the coagulable 

 albumin (including the residue remaining undissolved) in the mixture of 

 the digestion products, then we have a check on the correctness of the 

 analysis : the sum of these values and the albumoses must equal the quan- 

 tity of the albumin used. 



