IX. 

 QUANTITATIVE DIGESTION EXPERIMENTS. 



For a short series of experiments fresh fibrin and coag- 

 lated egg -albumen may be used; for a longer series only 

 material containing a fixed amount of water can be used. 

 For example, fibrin which has been treated with alcohol 

 and ether and then powdered, coagulated egg -albumen 

 treated with alcohol and ether, etc. In any case, care must 

 be taken that, in any series of experiments, the same material 

 is always used. This should be prepared beforehand in 

 large quantities, and it must be kept in closed vessels, since 

 the amount of water which it contains must not change. 

 Blood-serum which has been preserved by the addition of 

 chloroform may also be used. 1 The chloroform must be 

 expelled by means of an air-current before using the serum. 

 The results are not quite equivalent, but depend upon the 

 nature of the material used. Slight disturbing influences 

 do not often appear when fresh fibrin is used, but only when 

 hard-boiled egg-albumen is used. Furthermore, weak dis- 

 turbing influences are sometimes more perceptible when 

 pepsin-hydrochloric acid is used than when the extract of 

 the lining of the stomach is made use of. Finally, the dura- 

 tion of the digestion is also of influence. It is often neces- 



1 Fluid egg-albumen can no longer be used, since we have learned that 

 it contains ovomucoid, which necessarily causes an error when we base our 

 opinion regarding the digestibility on the quantity of the portion dis- 

 solved during the digestion. 



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