Metabolism; Digestion and Translocation 277 



ubility of another portion of the gluten in 70 per cent alcohol 

 and save the solution. Use a part of this solution for an obser- 

 vation upon coagulation by diluting the part taken to three times 

 the volume with distilled water. 



Grind up three grams of beans extracted with 30 cc. of water 

 in a test-tube, shake occasionally for 10 minutes, filter, and 

 employ the nitrate along with the preceding solutions in some 

 of the tests given below. A portion of this filtrate, however, 

 may be tested as to coagulation in two ways : (a) acidulate a 

 small amount in the test-tube and apply heat ; (6) add to a 

 few cubic centimeters in a test-tube four times the volume of 

 95 per cent alcohol. 



The following are some reactions of proteins which are in 

 part distinctive : - 



1. Brick or rose-red color with Millon's reagent on standing, 

 or with gentle heat. [To prepare Millon's reagent dissolve 1 

 gram of mercury in 2 grams of nitric acid (1.42 s. g.), and then 

 dilute with twice the volume of water.] 



2. The Biuret reaction, a violet or purple color with copper 

 sulfate and sodium hydrate. To a very weak copper sulfate 

 solution add excess of potassium hydrate and apply heat, then 

 add a small amount of a protein solution and heat again. 



3. Yellow color on boiling with nitric acid, the xanthoproteic 

 reaction. After boiling, cool under the faucet and add ammonia, 

 when the color will change to orange. 



4. Violet color with acetic and sulfuric acid. Use 2 parts 

 glacial acetic and 1 part sulfuric acid, with a small amount of 

 protein material, and apply gentle heat. 



Starch digestion. - - Several forms of diastase may be obtained 

 as commercial products, but it is well to undertake the extraction 

 of one or more of these in the laboratory. Take 200 grams of 

 clean barley seed, soak in running water over night, and germi- 

 nate in a thick layer over moss until the roots are about 1 inch 

 long and the plumules well started. Dry at 40 or 50 C. for 

 about six hours. From this malt the diastase of secretion is to be 

 obtained. In the same way collect (preferably an hour or two 

 at least after sunset) about 200 grams of nasturtium, bean, or 



