406 PRACTICAL PHYSIOLOGY 



EXPERIMENT X. Preparation and reactions of Indol, Skatol and 

 Phenol. Prepare an artificial digestion mixture with pancreatic 

 extract, or minced pancreas, and allow it to incubate without the 

 addition of an antiseptic, until it has an intense and disagreeable 

 odour. The digest is then acidified with acetic acid and placed in 

 a large flask connected with a Liebig condenser. Distillation is 

 continued as long as the distillate has a marked odour. (Indol 

 distils over much more quickly than skatol). The following tests 

 are then applied to portions of the distillate : 



Indol. 1. Legal's Test. To a few c.c. of the solution in a test 

 tube add a few drops of sodium nitro-prusside solution and then 

 ammonia till alkaline. A deep reddish violet colour results, which 

 changes to blue on acidifying with acetic acid. 2. Add to a few 

 c.c. of the liquid about 2 c.c. of each of the following solutions : 

 (i) Para-dimethyl-amino-benzaldehyde 4 parts, 95 per cent, alcohol 

 380 parts, hydrochloric acid (cone.) 80 parts, (ii) Potassium persulphate 

 2 grams in 100 c.c. water; a reddish pink colour results. 



Skatol. Warm some of the solution with an equal volume of 

 strong sulphuric acid. A red colour results. 



Phenol. Boil some of the solution with Millon's reagent. A red 

 colour, but no precipitate results. 



The action of bacteria on carbohydrates is even more energetic than 

 it is on proteins. They can do all that ptyalin and amylopsin can do, 

 but besides this they can decompose the monosaccharides into simpler 

 bodies such as ethyl alcohol, lactic and butyric acids. They have 

 also the power of digesting cellulose whereby methane (CH 4 ) is pro- 

 duced as one of the products. 



On fats they act like steapsin, but here also they can carry the 

 process a stage farther in that they transform the fat acid, which 

 is first of all liberated, into members lower in the fat acid series. 

 They decompose lecithin, and prevent the poisonous action of the 

 liberated cholin by further breaking it up into carbon dioxide, 

 methane and ammonia. 



The meconium of the foetus l is sterile, but very shortly after birth 

 micro-organisms gain admission to the intestine with the food. The 

 exact varieties of organisms present in the intestine depends mainly 

 on the nature of the food and on the presence of oxygen. The 

 anaerobic bacillus putrificus is the most important proteoclastic 

 organism, its action being supplemented by the aerobic B. coli and 

 B. lactis aerogenes, i.e. the latter organisms act on the products 



1 Meconium is a substance which collects in the intestines during intra-uterine 

 life. 



