DEFENSE AGAINST ORGANIC POISONS 243 



A host of other aromatic organic substances are similarly combined 

 with sulphuric acid,^* with or without preliminary oxidation, includ- 

 ing all substances resembhng phenol or which through oxidation are 

 changed into phenols, such as cresol, thymol, anilin, naphthalin, pyro- 

 gallol, and tannin. By this means a poisonous substance is converted 

 into a relatively harmless one, which is readily soluble and rapidly 

 eliminated. 



2. Glycuronic acid occupies the same position as sulphuric acid, com- 

 bining particularly with naphthol, thymol, camphor, chloral hydrate, 

 and but}'! chloral. Sometimes a substance may appear in the urine 

 combined in part with sulphuric, in part with glycuronic acid, show- 

 ing the similarity of their function. Apparently when there is not 

 sufficient sulphuric acid in the body to combine with all the poison, 

 the excess unites with glycuronic acid,^^ although combination between 

 glycuronic acid and the aromatic substance begins to occur before all 

 the sulphuric acid is exhausted. ^"^ Glycuronic acid represents merely 

 a first step in the oxidation of glucose, as follows : 



OHC-(CHOH)4-CH20H + 00 = 0HC-(CH0H)4-C00H + H2O. 

 (glucose) (glycuronic acid) 



This oxidation occurs after the aldehyde group of the glucose has 

 been combined by some other substance; hence the aldehyde group 

 escapes oxidation, although ordinarily more easily oxidized than the 

 alcohol group. 



Just as with the addition of sulphuric acid, oxidation may be a 

 preliminary step to the addition of glycuronic acid; e.g., naphthalin 

 is oxidized into a-naphthol, before uniting to glycuronic acid, as fol- 

 lows: 



H H 

 /C=C\ H H H 



HC4 ^C-C^ /C = C\ OH 



^C-Cf >CH + O = HC< >C-C^ 



H \C = C/ ^C-Cf >CH 



H H H \C = C/ 



H H 

 (naphthalin) (a-naphthol) 



The same is the case with many camphors and terpenes. Reduction 

 may be the preliminary step, as with chloral hydrate, which is first 

 reduced to trichlor-ethyl-alcohol. In still other cases splitting off of 

 water is the chief preliminary step. 



3. Glycine is one of the longest known combining substances, the 

 observation of the combination of glycine with benzoic acid to form 

 hippuric acid being the first proof of synthesis in the animal body dis- 

 covered by Wohler (1824). The reaction is as follows: 



CeHsCOOH + H2N-CH2-COOH = C6H5CO-HN-CH2-COOH + H2O. 

 (benzoic acid) (glycine) (hippuric acid) 



28 3gg Hammarsten's Text-book (fourth American ed.). P- 542. 



28 See Austin and Barron, Boston Me^. and Surg. Jour., 1905 (152), 269. 

 Wohlgemuth has observed a case in which all the sulphuric acid of the urine was 

 in organic combination (Berl. klin. Woch., 1906 (43), 508). 



30 See Salkowski, Zeit. physiol. Chem., 1904 (42), 230. 



