BY DR. LAUDER BRUNTON. 519 



fibrin in a large test-tube, pour off the water, add artificial 

 pancreatic juice or glycerin extract of pancreas, and put the 

 tube in the water-bath at 40 C. At first it will not be altered, 

 but after two hours or more the bits will be found to be easily 

 torn by stirring, and the smaller ones will disappear, and if 

 two or three are taken out and washed with water they will 

 be seen to be corroded, not swollen as in gastric juice. To 

 show that the coagulated fibrin has been converted by the 

 pancreatic juice into a body resembling raw fibrin in its pro- 

 perties, put a bit into O.I per cent, of hydrochloric acid. It 

 dissolves veiy quickly, forming a solution of syntonin. Rub 

 up a second bit with 10 per cent, salt solution, and filter. The 

 filtrate contains albumin in solution. Add nitric acid to one 

 portion of it and boil another; a precipitation occurs in both. 

 If boiled fibrin is tested in the same way, it is found to be 

 insoluble in these reagents. Even raw fibrin is much less solu- 

 ble than the boiled fibrin which has been acted on by pancreatic 

 juice. 



Take part of the solution of fibrin in pancreatic juice and 

 boil it. Neutralize another portion with acetic acid; a precipi- 

 tate is formed in both. Let the rest stand for two or three 

 hours longer, then acidulate it with acetic acid and boil, to 

 coagulate any albumin present. Filter. Evaporate the filtrate 

 at 60 to TO 6 C., and add alcohol to it while still hot, till the 

 peptones are precipitated. Let it stand for twenty-four hours 

 and filter. Dissolve the precipitate of peptones in water and 

 apply the tests given in 118. Evaporate the filtrate to a 

 moderately small bulk and let it cool. Tyrosine crystallizes 

 out. Pour off the mother liquor, evaporate it to a sraa.ll bulk, 

 and leucine will crystallize out. In order to purify the tyro- 

 sine, put it on a filter and wash it, first with ice-cold water till 

 the filtrate is colorless, and then with spirit, next with abso- 

 lute alcohol, and lastly with ether. To purify the leucine, put 

 the crystals on a filter, which must be allowed to stand in a 

 cool place until not a drop more runs from it. Then wash it, 

 first with ice-cold water until the filtrate is colorless, next 

 with common alcohol, then with absolute alcohol, and lastly 

 with ether. It is of great importance that the mother liquor 

 should be allowed to drain away completely before the wash- 

 ing, as otherwise the crystals would dissolve in the water used. 

 Test the mother liquor for naphthilamine and indol. In test- 

 ing for the former, dilute naphthilamine is indicated b}' the 

 appearance of a rose-red color when chlorine water is added 

 gradually to the mother liquor diluted with water. To prove 

 the presence of indol, dilute some of the mother liquor, boil it 

 in a test-tube, add a little dilute sulphuric acid and a drop or 

 two of a dilute solution of a nitrite; or of very dilute nitrous 

 acid, a red color is produced. The dilute nitrous acid for this 



