312 PRACTICAL PHYSIOLOGY 



test for sulphur. A fair yield of tyrosine may be had from the original 

 mother liquor. 



Preparations of trypsin have a rennin-like action on milk if sufficient 

 calcium be added (see p. 232). 



Intestinal Juice. Succus Entericus. This is secreted by Lieber- 

 kuhn's follicles. 



'Extracts of the mucous membrane of the intestine, prepared by 

 scraping this off and grinding it with sand and water and then filtering 

 through muslin, usually contain large amounts of ferments. This 

 extract will contain both exoenzymes and endoenzymes. 



To Demonstrate the Ereptic Power of Tissues. Take 20 gms. 

 minced liver, and 20 gms. mucous membrane of the intestine 

 (scraped off with a scalpel). Grind each in a mortar with fine quartz 

 sand and 20 c.c. of a 0-2 per <%: t. solution of Na 2 CO 3 . Filter the 

 extracts through muslin. Divide each extract into two equal parts, 

 A and B. To A of each extract add 1 c.c. of a 2-5 per cent, solution of 

 Witte's peptone, and to B a similar amount of a 2-5 per cent, solution of 

 egg-white. Remove a few drops of the contents of each of the four 

 test tubes, and apply the Biuret test, noting the results. Place the 

 tubes in the incubator at body temperature, and at the end of an hour 

 again remove a little of the contents of each tube, and apply the Biuret 

 test. It will be found that there is no change in the tube (B) containing 

 egg-white, but that in the tube (A), containing the intestinal extract, 

 the test has become very feeble or disappeared entirely. By longer 

 incubation, the Biuret secretion will also disappear from the tube (A) 

 containing liver. 



By thus ascertaining the time required to split up a standard solution 

 of peptone, so that the Biuret test is no longer given, a comparative 

 estimate may be made of the ereptic power of different extracts. 



Separation of Bile Salts. 'Thoroughly mix 50 gms. pure animal charcoal 

 with 200 c.c. of ox-bile in an evaporating dish, and evaporate the mixture 

 to dryness on a waterbath. During the drying the mixture should be 

 frequently stirred. The black powder thus obtained can be kept a 

 considerable time. To extract the bile salts from it, mix it with 

 absolute alcohol in a flask and place the flask on the boiling waterbath 

 for about a quarter of an hour, cool, filter into a dry cylinder, and 

 add anhydrous ether to the filtrate till a permanent haze is produced. 

 Now cover the cylinder with a ground glass plate, and allow it to stand 

 in a cool place till next day, when it will be found that a crystalline 

 mass of bile salts has separated out (Plattner's Crystalline Bile). The 

 crystals can now be collected on a filter paper and allowed to dry in a 

 desiccator. 



A 1 per cent, solution of the crystals should now be made, and 

 Pettenkofer's reaction (see p. 236) applied to it by the following method : 



Dissolve a few grains of cane-sugar in the solution, and run con- 

 trated sulphuric acid down the side of the tube so as to form a layer 

 underneath the watery solution. A violet ring is formed where the 

 two fluids meet. Now place the test tube in a beaker of cold water, 

 and shake gently so as to mix the two fluids. A violet solution is thus 

 obtained. (By cooling the test tube in water too great a rise of 

 temperature is avoided.) Divide the violet solution into two parts, 

 A and B. Add A to some ether and examine by means of the spectro- 

 scope a distinct band is seen in the green. Add B to some absolute 

 alcohol and note that, although the spectrum is at first the same as in A, 



