substances are precipitated? Gather the precipitate together with 

 a glass rod so far as possible and filter the remainder of the 

 mixture through a dry filter. This filtrate contains the ainino 

 acids. Concentrate to a syrupy consistency, transfer to a flask and 

 allow to stand until next day for crystallization. Crystals of leucin 

 and ty rosin separate out. Examine under microscope, identify 

 and draw. 



91. Examine the preparations of amino-acids ; glycocoll, tyrosin, 

 leucin. Test water-solubility, coagulation by heat and response to 

 protein color reactions ( xanthoproteic, Millon's, biuret). Note 

 carefully differences from and resemblances with protein. 



92. Vegetable protease. Broiiielin. Cut a pineapple into 

 small portions and express the juice into a mortar. Filter. Test 

 the reaction of filtered juice. Place strips of fibrin in four test- 

 tubes and add as follows: to a: filtered juice (unaltered) ; to 1) : the 

 same, exactly neutralized with o.2 c /f KOH ; to c: the same made 

 alkaline with an equal volume of \','< Na^CO, ; to d: pineapple 

 juice previously boiled. Place at 40 and examine at intervals 

 as with'other ferments. Note carefully any differences from pepsin 

 or trypsin. In which tube is digestion most rapid? After 40 minutes 

 remove the undigested fibrin from each tube and test for peptone 

 by the biuret reaction. 



II. COAGULATING ENZYMES. 



93. Reniiin. Place 10 cc. of milk in each three test-tubes. 

 To a add 3 cc. rennin solution ; to b the same, previously boiled ; 

 to c add a few cc. dilute NH 4 oxalate solution and then 3 cc. rennin 

 solution. Place at 40 for 15 minutes, examining at intervals. Re- 

 sult? After 20 minutes add a few drops CaCL solution to c. Result? 

 Explain. 



III. OXIDIZING AND REDUCING ENZYMES. 



94. Catalase. To 5 cc. neutralized hydrogen peroxide (H,O.,) in 

 a test-tube add about 3 cc. crushed liver suspension. Note result. 

 \Yhat is the reaction? Repeat using liver which has previously 

 been boiled. Result? Also (a) using a mixture of 5 cc. of liver 

 suspension and 5 drops of io c / c HC1, (b) 5 cc. of liver suspension 

 and i cc. of i ( /r- Na,CO,. (c) liver suspension plus equal vol. n/io 

 KCN solution, (d) liver suspension plus equal vol. saturated 

 HgCl, solution. In which of the above is an evolution of gas 



