376 INDOL SKATOL PHENOL. 



alkalies. Gelatin, under the same conditions, yields much leucin and 

 ammonia, C0 2 , acetic, butyric, and valerianic acids, and glycin (Nencki). 

 Mucin and nuclein undergo no change. Artificial pancreatic digestion 

 experiments rapidly tend to undergo putrefaction. 



The substance which causes the peculiar f secal odour is produced by putrefaction, 

 but its nature is not known. It clings so firmly to indol and skatol that these sub- 

 stances were formerly regarded as the odorous bodies, but when they are prepared 

 pure they are odourless (Bayer). The above-mentioned putrefactive processes, 

 which also occur in pancreas undergoing decomposition, may be interrupted by 

 antiseptics (salicylic acid). The putrefactive products of the pancreas give a red 

 colour or precipitate with chlorine water. 



Indol. Amongst the solid substances in the large intestine formed 

 only ly putrefaction is indol (CgH^N), a substance which is also formed 

 when proteids are heated with alkalies, or by overheating them with 

 water to 200C. 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. Landois observed the same after the transfusion 

 of heterogeneous blood. 



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-proprionic acid, much indican was present in the 

 urine. 



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

 is also formed when fibrin and pancreatic juice putrefy outside the 

 body (Baumann), while Brieger found it constantly in the fseces. It 

 seems to be increased by the same circumstances that increase indol 

 (Salkowski), as an excess of indican in the urine is accompanied by 

 an increase of phenylsulphuric acid in that fluid. 



Hydrocinnamic acid (phenylpropionic acid) may also be obtained from putre- 

 fying flesh and fibrin. It 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 (E. and H. Salkowski). 



Skatol (C 9 H 9 N = methylindol) (Brieger), 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 sulphuric acid com- 

 pound. The excretin of human faeces, described by Marcet, is related 

 to cholesterin, but its history and constitution are unknown. 



