282 REACTIONS FOR INDOL. 



seen that pancreatic digestion acts upon the proteids, forming, among other 

 products, amido-acids, leucin, tyrosin, and other bodies ( 170, II.). Under normal 

 conditions, this is the greatest decomposition produced by the pancreatic juice. 

 The putrefactive fermentation of the large intestine causes further and more 

 profound* decompositions. Leucin (C 6 H 13 N0 2 ) takes up two molecules of water 

 and yields valerianic acid (C 5 H 10 O 2 ), ammonia, C0. 2 and 2(H 2 ) ; glycin behaves 

 in a similar manner. Tyrosin (C 9 H u N0 3 ) is decomposed into indol (C 8 H 7 N), 

 which is constantly present in the intestine along with C0 2 ,H 2 0,H. If O be 

 present, other decompositions take place. These putrefactive products are absent 

 from the intestinal canal of the foetus and the newly-born. During the putre- 

 factive decomposition of proteids, C0 2 , H 2 S, H, and CH 4 , are formed ; the same 

 result is obtained by boiling them with alkalies. Gelatin, under the same con- 

 ditions, yields much leucin and ammonia, C0 2 , acetic, butyric, and valerianic 

 acids, and glycin. Mucin and nuclein undergo no change. Artificial pancreatic 

 digestion-experiments rapidly tend to undergo putrefaction. 



The substance which causes the peculiar fsecal odour is produced by putrefaction, but its 

 nature is not known. It clings so firmly to indol and skatol that these substances were 

 formerly regarded as the odorous bodies, but when they are prepared pure they are odourless 

 {Bayer). 



Amongst the solid substances in the large intestine formed only by putrefaction 

 is indol (CgH^N), a substance which is also formed when proteids are heated with 

 alkalies, or by superheating them with water to 200 C. It is the stage preceding 

 the indican in the urine. If the products of the digestion of the proteids the 

 peptones are rapidly absorbed, there is only a slight formation of indol; but 

 when absorption is slight, and putrefaction of the products of pancreatic digestion 

 occurs, much indol is formed, and indican appears in the urine. 



Jaffe found much indican in the urine in strangulated hernia, and when the small intestine 

 was obstructed. 



Reactions for Indol. Acidulate strongly with HC1, and shake vigorously after adding a few 

 drops of turpentine. If there be an intense red colour, the pigment is removed by ether. 

 The substance which is formed after the digestion of fibrin by trypsin, and which gives a violet 

 colour with bromine water ( 170, 2), can be removed by chloroform. In addition to the last 

 pigment, there is a second one, which passes over during distillation, and which can be extracted 

 from the distillate by ether. Both substances seem to belong to the indigo group (Krukenberg). 



A. Bayer prepared indigo-blue artificially from ortho-phenyl-propionic acid, by boiling it 

 with dilute caustic soda, after the addition of a little grape-sugar. He obtained indol and 

 skatol from indigo-blue. Hoppe-Seyler found that on feeding rabbits with ortho-nitrophenyl- 

 propionic acid, much indican was present in the urine. 



Phenol (C 6 H 6 0) is formed during putrefaction in the intestine, and it is also 

 formed when fibrin and pancreatic juice putrefy outside the body, while Brieger 

 found it constantly in the faeces. It seems to be increased by the same circum- 

 stances that increase indol, as an excess of indican in the urine is accompanied by 

 an increase of phenylsulphonic acid in that fluid ( 262). 



From putrefying flesh and fibrin, amido-phenylpropionic acid is obtained, as a decomposition- 

 product of tryrosin. A part of this is transformed by putrefactive ferments into hydrocinnamic 

 acid (phenylpropionic acid). The latter is completely oxidised in the body into benzoic acid, 

 and appears as hippuric acid in the urine. Thus is explained the formation of hippuric acid 

 from a purely albuminous diet. 



Skatol (C 9 H 9 N = methylindol) is a constant human faecal substance, and has 

 been prepared artificially by Nencki and Secretan from egg-albumin, by allowing 

 it to putrefy for a long time under water. It also appears in the urine as a 

 sulphur compound. The excretin of human faeces, described by Marcet, is 

 related to cholesterin, but its history and constitution are unknown. 



According to Salkowski, skatol and indol are both formed from a common substance which 

 exists preformed in albumin, and which, when it is decomposed, at one time yields more indol, 

 at another skatol, according as the hypothetical " indol-fungus" or " sTcatol-fungus" is the 

 more abundant. 



