46 METHODS OF SEPARATING SOLUBLE PRODUCTS. [BOOK IL 



carried on in a tube of parchment paper, which is surrounded by 

 liquid which is kept at a constant temperature, the tube being also 



FIG. 3. DB SHERIDAN LEA'S APPARATUS FOR SEPARATING BY MEANS OP DIALYSIS, THE 

 PRODUCTS OF DIGESTION, AND FOR KEEPING THE DIGESTIVE MIXTURE IN MOTION. 



subjected to a continuously recurring movement, so as to imitate as 

 nearly as possible the conditions which exist in the alimentary canal. 

 " By means of this apparatus a distant and incomplete approxi- 

 mation to two of the more important conditions under which normal 

 digestion takes place may be realised, viz., continuous movement and 

 removal of digestive products. The substance to be digested is 

 placed inside the dialyser-tube (i) together with the digestive fluid ; 

 (g) is filled up to the level of the tubulure (c) with a fluid similar in 

 composition to that which is in (i) but minus any ferment, and the 

 contents of (g) and (i) are maintained at any desired digestive 

 temperature by means of the current of water which flows through (a). 

 Finally, the dialyser-tube is kept in constant motion by the string 



(&)" " 



"The mixing of the contents of (i) is very perfect, waves which 

 might almost be called ' peristaltic ' running up the flexible walls of 

 the dialyser-tube each time it is suddenly lowered after its more 

 gradual ascent. The removal of the digestive products is on the 



