PANCREATIC DIGESTION. 95 



Leucin (amido-caproic acid), 



(CH 3 ) 2 CHCH 2 CH(NH 2 )COOH, 



and tyrosin (para-oxy-phenyl-alpha-amido-propionic acid), 

 C 6 H 4 OHCH 2 CH(KE 2 )COOH, 



are formed in the decomposition of protein substances by 

 putrefaction as well as in the normal processes of digestion, 

 and hence they may be found as a result of pathological 

 processes where there is a destruction of the proteins. 

 Leucin crystallizes in the form of thin plates, which are 

 usually, when impure, grouped together into round knobs 

 or balls. These can be recognized by the aid of the micro- 

 scope. (Plate II, 12, &.) In the impure state tyrosin forms 

 aggregations of crystals which resemble those of leucin, but 

 when purified it appears as fine silky needles often gathered 

 into sheaves or balls. (Plate II, 12, c.) Tyrosin requires 

 for its solution 2454 parts of water at 20. Leucin can be 

 dissolved in 27 parts of cold water. This affords a means 

 of separating them. 



209. In a series of test-tubes place a small amount 

 of pancreatic extract, prepared as in Experiment 210. Boil 

 one (A); acidify the second (B) with hydrochloric acid; 

 make the third (C) slightly alkaline with sodium carbo- 

 nate; make the fourth (D) neutral if it is not already so. 

 Place in each a shred of fibrin and set the tubes in water 

 at 40. Let a fifth tube (E) be made alkaline and stand 

 with fibrin in cold water. Note the change in the appear- 

 ance of the fibrin and the speed of digestion. If the tubes 

 are to be left for a long time putrefaction can only be pre- 

 vented by the use of some antiseptic like chloroform water 

 (chloroform, 5; water, 1000) or thymol. 



Is solution caused by an enzyme? What conditions 

 most favor it? 



