ELEMENTARY PHYSIOLOGICAL CHEMISTRY 231 



especially interesting because it contains, besides an amido group, a 

 sulphur group. It is probably the source of the taurin of the bile (see 

 CH - SH P' 4^6) and sometimes appears in the urine (see. p. 279). 



Cystin, it will be seen, is related to lactic acid. 



CH -NH 2 The hexone bases are the only decomposition pro- 



ducts obtainable from protamines (Kossel's first group) ; 

 if amido acids be also produced we have the albuminoids 

 (Cystin.) (second group) ; if aromatic bodies tyrosin be also pro- 

 duced, we have true proteids (third group) ; and if either of these three 

 groups be in combination with other bodies, such as nuclein or carbohy- 

 drate, we have the compound proteids (fourth group). (See also Proteids.) 



II. Amylopsin. This acts on starch in exactly the same way as 

 ptyalin does i.e. it converts it into maltose. It can, however, also 

 digest cellulose, 1 so that it is capable of acting on unboiled starch. 



EXPERIMENT IX. Add some glycerine extract of pancreas to some 

 powdered starch. Shake, and place in the water-bath at 37. Remove 

 drops every half minute, and mix on a slab with a drop of iodine solu- 

 tion. Note the appearance of the dextrine reaction. When this dis- 

 appears apply Trommer's test to a sample of the digest; note the 

 reduction due to maltose. 



III. Steapsin. This decomposes neutral fat into fatty acid and 

 glycerin. (See Fats, p. 180.) 



EXPERIMENT X. Some minced pancreas is shaken with water 2 and 

 the resulting extract divided into two parts. One of these is boiled to 

 destroy the ferment and is then cooled. To each portion (about 10 c.c.) 

 are added five drops of melted and filtered butter fat, a few drops of an 

 alcoholic solution of phenolphtalein and then n/ lo NaOH until a deep 

 red colour is obtained. After vigorous shaking so as to obtain a partial 

 emulsion the test-tubes are placed in the incubator, and, after about half- 

 an-hour, examined. The steapsin-containing fluid will be decolourised 

 (the fatty acid having bleached the phenolphtalein), and, to regain the 

 original red colour, a certain number of c.c. n/ lQ NaOH must be added 

 to it. In this way an approximate estimate can be obtained of the 

 fat-splitting power of the extract. 



The liberated fatty acid combines with the free alkali of the pan- 

 creatic juice and bile to form a soap, which is absorbed into the epithelial 

 cells of the villi, wherein it is again set free, and recombines with 

 glycerin to form neutral fat. 



IV. Milk Curdling Ferment. Extracts of pancreas cause milk to 

 clot ; but, in normal digestion, since the rennin x)f the stomach has 

 already produced this, the ferment can hardly ever come into play. 



1 This digestion of cellulose is, however, probably carried out chiefly by bacteria. 

 2 Glycerin does not dissolve steapsin, so that a glycerin extract of pancreas is 

 not suitable for this experiment. 



