% BY DR. LAUDER BRUNTON. 521 



remains suspended by filtration through Swedish paper. Re- 

 move the collodion from each precipitate by agitating it with 

 ether several times, and then diy it in vacuo. Treat the 

 yellowish residue (which consists of an admixture of coagu- 

 lated albumin with that pancreatic ferment which acts on 

 fibrin) with cold water, and filter. The ferment will be dis- 

 solved and the albumin left. Test the digestive power of the 

 filtrate on a bit of fibrin. 



Evaporate the filtrate (a) in vacuo, filter from the collodion 

 that separates, heat to 43-44 C. in a water-bath, in order to 

 separate an albuminous body contained in it which coagulates 

 at this temperature. Filter ; evaporate the filtrate in vacuo to 

 one-sixth of its bulk, and add a large quantity of absolute 

 alcohol. It is advisable to let the precipitate thus produced 

 remain under the alcohol for some days, as it is thus rendered 

 more insoluble in water. Collect the precipitate on a filter, 

 and wash it several times with strong spirit. Then treat it 

 with a mixture of one part of strong spirit and two parts water, 

 in order to dissolve the ferment and leave the albumin. Filter ; 

 evaporate the filtrate to dryness in vacuo, and dissolve the 

 residue in water. The solution converts starch quickly into 

 sugar, and digests fibrin, but not very quickly, the ferment 

 having this latter action not having been completely removed 

 by the collodion. It contains also leucine and tyrosine, but 

 the greater part of these may be removed by dialysis at 4 C. 

 The ferment should then be dried in order to keep it. 



171. Preparation of Tyrosine by Pancreatic Diges- 

 tion. Take out the pancreas of an animal which has been fed 

 five or six hours before being killed, weigh it, cut it in small 

 pieces, and rub it up with ten times its weight of raw fibrin, 

 and add to the whole twelve or fifteen parts of water at 45C. 

 Keep the whole at this temperature for four to six hours, 

 stirring frequently ; then add a little acetic acid, and boil to 

 coagulate albumin. Filter through a piece of linen, and evapo- 

 rate the filtrate quickly to a syrup. Pour it, while still hot, 

 into a flask, and add strong spirit to it till a distinct flocculeut 

 precipitate occurs. Let it cool ; filter, and distil the filtrate 

 till it forms a thick pulp while still warm. Let it stand for a 

 day in the cold to allow complete crystallization to take place ; 

 then throw it on a filter, and let the mother liquor drain com- 

 pletely away ; wash the residue with a little cold water, and 

 then put it into a large quantity of water at 50 C., which will 

 dissolve the leucine and leave the t} r rosine. Dissolve the 

 tyrosine in hot water, let it crystallize out, and then dissolve 

 it again in ammonia and re-crystallize. 



