222 COMPOSITION OF THE DIGESTIVE JUICES. [CH. VIII. 



The remaining 50 cc. of the solutions may be treated with 5 cc. 

 of the A mercuric nitrate solution (p. 391) and filtered. On examining 

 the clear filtrates polarimetrically it will be found that the rotation 

 in E is less than in F, owing to the fact that the specific rotatory 

 power of glucose is less than that of maltose. 



It is usually possible to demonstrate the presence of glucose in 

 E by the author's method, using blood charcoal. Five cc. of the 

 two solutions are diluted with 15 cc. of water, and the parallel tests 

 conducted as described in Ex. 381. 



267. Lactase. Repeat the above exercise, using a 2 per cent, 

 solution of lactose instead of the maltose. The osazone method 

 usually gives a definite result, as does the method with blood char- 

 coal. Polarimetric observations are of little use with lactose, owing 

 to the fact that the rotation of the solution is only slightly changed 

 by the hydrolysis of lactose. 



268. Sucrase (Invertase). To 20 cc. of 2 per cent, sucrose add 

 5 cc. of the intestinal extract and a little toluol ; shake, label, 

 stopper and incubate for 24 to 48 hours. Perform a control experi- 

 ment by first boiling the extract. 



Examine the two solutions for reducing sugar, which appears 

 as the result of the action of the enzyme. 



J. Bacterial decomposition in the intestine. 



A large number of micro-organisms are common 

 inhabitants of the intestine, being especially abundant in 

 the colon. Their growth and activities are dependent on a 

 variety of conditions, such as reaction, supply of food 

 materials, etc. It is probable that the changes induced, 

 even by a specific organism, are affected by the action of 

 other bacteria. For example, the fermentation of carbo- 

 hydrates to lactic and other acids by certain organisms 

 may inhibit the growth or modify the chemical activities 

 of other types. 



It is not possible to give here a full account of the 

 various changes brought about by bacteria in the intestine, 

 but certain of the products formed by the putrefaction of 



