CONJUGATED EXCRETA 555 



conjugates with glucuronic acid are harmless. Upon boiling with 

 dilute acids or occasionally even on allowing urine to stand, they 

 decompose, setting free glucuronic acid and the associated radical of 

 the conjugate. 



The origin of the glucuronic acid in urine is unknown. The most 

 natural assumption is to suppose that the toxic substances which are 

 eliminated in this way combine in the body with glucose, and that the 

 oxidation of glucose is by this so hindered, that it only proceeds as 

 far as the conversion of the primary alcohol-group into a carboxyl- 

 group. Certainly the phenyl-glucuronic acid is a compound of the 

 glucoside type, i. e., the phenyl radical is attached to the glucu- 

 ronic acid by the aldehyde-group. On the other hand if camphor be 

 administered in large amounts to phloridzinized dogs, although the 

 excretion of glucuronates is very greatly increased thereby, the excre- 

 tion of glucose is either not diminished at all or only slightly diminished, 

 a fact which would appear to indicate some other source than glucose 

 for the glucuronic acid. 



A very important excretory conjugate is the conjugated sulphuric 

 acid, indoxyl-sulphuric acid or Indican: 



C.O.SOzOH 



/\ -'- 



C 6 H 4 CH 



NH 



which yields Indigo when treated with oxidizing agents. This substance 

 arises by conjugation of indoxyl with sulphuric acid and is the form in 

 which the greater part of the indoxyl output is present in the urine. 

 The indoxyl output varies with the extent of putrefactive processes 

 in the intestine. Any measure of Intestinal Stasis, such as that induced 

 by tying off a loop of small intestine, results in an increase of the 

 indican output. The subcutaneous injection of indol leads to an 

 increased output of indican, while the administration of an excess of 

 Tryptophane in this way does not. Evidently the tissues do not decom- 

 pose tryptophane in such a way as to liberate indole, while the intes- 

 tinal bacteria, like the majority of putrefactive bacteria, generate a 

 large proportion of indole from tryptophane, which, after absorption 

 is oxidized to indoxyl and then excreted in the form indicated above. 

 It must be remembered that the indican output, although generally 

 running parallel with the degree of intestinal stasis or putrefaction, is 

 not a reliable measure of intestinal putrefaction when taken by itself, 

 for the output depends, not solely upon putrefaction, but also upon 

 the proportion of tryptophane which is contained in the proteins of 

 the diet. Thus, if a large part of the protein intake be supplied by 

 Gelatin, which contains no tryptophane, the indican output becomes 

 very small although putrefactive processes may not be diminished in 



