VIII] THE PROTEINS AND PROTEASES 185 



crystals. To obtain better crystals, filter off the edestiu tliat has been deposited, and 

 pour the filtrate into a dialyzer ; add a little toluol, and svis[)end the dialyzer in 

 running' water. As soon as it is cloudy, examine the dialyzed solution for crystals 

 under the microscoi)e. Add a little 5"/,, sodium chloride solution to the original 

 precipitate of edestiu in the filter. Make with the filtrate the following tests : 

 (i) The tests for proteins [Expt. 121, {ay{d), except Millon's]. (ii) Boil a little of the 

 solution : it is imperfectly coagulated, (iii) Add a little acid : edestin chloride is 

 precipitated. 



In the Castor-oil seed (Ricinus communis) there is also present a 

 globulin which can be obtained in a crystalline form by the method of 

 Expt. 134. In addition, there is present an albumin, ricin, which has 

 peculiar toxic properties (Osborne, 8). 



A well-crystallized globulin can be obtained from the Linseed (Linura 

 lositatissimum), and a globulin, excelsin, from the Brazil nut (Bertholletia 

 excelsa) also in crystalline or semi-crystalline form. Similar globulins 

 can be extracted from a number of other seeds, i.e. Coconut (Cocas 

 nacifera), Sunflower (Helianthus annuus), Cotton-seed {Gossypiuni her- 

 baceum), Mustard-seed (Brassica alba) and many others. The fat is first 

 removed from the ground seed by ether or benzene ; the residue is then 

 extracted with dilute sodium chloride and the extract dialyzed. 



Expt. 134. Extraction of the glohuUn from Ricinus. Weigh out about 50 gms. of 

 Ricinus seeds, take off the testas and pound in a mortar. Extract the oil by the 

 method given in Expt. 82. After extracting the oil, grind up the residue again in a 

 mortar, and then treat it with about twice its bulk of 10 % sodium chloride solution 

 for 6-12 hrs. Filter successively through muslin and filter-paper and dialyze the 

 filtrate. The globulin will be precipitated in semi-crystalline spheroids. When 

 the bulk of the globulin has separated out, filter off the precipitate, and dissolve it 

 in as dilute a sodium chloride solution as possible. Make the following tests with 

 the solution: (i) The tests for proteins [Expt. 121, {a)-{d\ except Millon's]. (ii) Boil 

 a little of the solution : the coagulation is not complete, (iii) Add a little hydrochloric 

 acid : a precipitate is formed. 



Expt. 135. Extraction of the globulin front. Linseed (Osborne, 7, 8). Weigh out 

 about 50 gms. of Linseed and grind it in a coffee-mill. Extract the oil as in Expt. 82. 

 Treat the residue with about twice its bulk of 10 "/d sodium chloride solution for 

 6-12 hrs. Then filter through muslin and filter- paper, and dialyze the filtrate. 

 The globulin separates out in octahedra. Filter off the protein, and take up in 

 dilute sodium chloride. Test the solution as in the case of Ricinus globulin in the 

 previous experiment. 



Expt. 136. Extraction of the globulin (excelsin) from the Brazil nut (Osborne, 8). 

 Weigh out about 100 gms. of the nut, free from the testas, and, after pounding in a 

 mortar, extract the oil by the usual method. Then proceed as in the two previous 

 experiments. The protein separates out in semi-crystalline si)heroids. Filter off" the 

 precipitated excelsin, and dissolve in dilute sodium chloride solution. Make with 

 it the tests as for the globulins in the last two experiments. 



