14 INTESTINAL DIGESTION. 



in the intestine ; the latter is decomposed, yielding leucin 

 and tyrosin and other products. 



Simultaneously with the changes which are due to the 

 action of the pancreatic ferments, others go on which are 

 associated with the development in the liquid of septic 

 organisms (bacteria), and with the disengagement of offen- 

 sive odours. These are the production of volatile bodies, 

 Indol and Skatol, the disengagement of CO 2 and CH 4 

 from "the decomposition of certain carbohydrates, of H 

 from butyric acid fermentation, &c. The products of 

 pancreatic digestion of proteids are also incidents of the 

 septic decomposition of the same bodies, but the former 

 process is distinguished from the latter by its great 

 rapidity. 



The liquid which is obtained when raw fibrin is digested for a few hours, 

 or at the proper temperature with pancreatic juice or solution of pancreatin, 

 contains, after it has been freed from undissolved residue, besides common 

 albumin, alkali-albuminate and peptones, crystalline organic bodies, of which 

 the most important are Leucin and Tyrosin. To obtain them, the albumin is 

 first got rid of by slightly acidulating the liquid, boiling and filtering. The 

 filtrate is then reduced to a small bulk by evaporation, and heated with strong 

 alcohol to precipitate the peptone. On again filtering, an extract is obtained 

 in which, if left to itself, Leucin and Tyrosin crystallize. 



Leucin (C 6 H I3 NO 2 ), when pure, crystallizes in colourless pearly scales, 

 which sublime in flocks at 170 C. like oxide of zinc. In impure solution it 

 forms spheroidal clumps, which, under the microscope, are seen to be made 

 up of round grains, each of which consists of fine needles radiating from a 

 centre. Tyrosin crystallizes, on cooling from its solution in boiling water, in 

 bunches or stellate groups of long slender needles ; it does not sublime when 

 heated. 



Leucin is soluble in 27 parts of cold water and in hot alcohol. Tyrosin 

 requires 150 parts of hot water to dissolve it. In boiling alcohol Leucin 

 dissolves, Tyrosin remains, so that by means of it the two bodies can be sepa- 

 rated from each other. Leucin, when heated in a sealed tube with fuming 

 hydriodic acid, yields ammonic iodide and caproic acid, and is therefore 

 regarded as amido- caproic acid (C 6 H 13 NO 2 -f 3HI = C 6 H 12 O 2 -f NH 4 

 I + 2l). Tyrosin (C 9 H n NO 3 ), when acted on in the same way, yields a body 

 (C 9 Hj O 3 ) which may be regarded as oxyphenylpropionic acid, having 

 ammonic iodide and iodine. The physiological destiny of Leucin is unknown. 

 As regards Tyrosin, the recent researches of Kiissner have shown that when 

 it is introduced into the circulation it reappears in the urine as such : it cannot 

 therefore be regarded as a step in the production of urea. 



