244 DEFENSE AGAINST NON-ANTIGENIC POISONS 



A special enzyme has Ijeen found in kidney substance vvliicli can bring 

 about this reaction outside the body. Normally this enzyme occurs 

 chiefly in the kidney l)ut may also occur in other organs. Man}' other 

 aromatic compounds also combine with glycine before elimination, 

 e. g., salicylic acid. Some are first altered to a suitable form by 

 oxidation; e. g., toluene is oxidized to benzoic acid, xylene to toluic 

 acid, nitro-benzaldehyde to nitro-benzoic acid. Many of the sub- 

 stances that can be made to combine with glycine in the body are of 

 such a foreign nature that they never could need neutralization under 

 any other than experimental conditions, but here, as with the sul- 

 phuric and glycuronic acid reactions, combination occurs whenever a 

 suitable substance is present in the blood, glycine alwa^'s being abun- 

 dant as a cleavage product of the proteins. 



4. Urea ma}' also be a means of defense, forming salts with organic 

 acids which are rapidly eliminated; e. g., amido-benzoic acid and nitro- 

 hippuric acid. 



5. Methane. — Methylation, which occurs also with tellurium, is 

 observed on administration of pyridine, as shown by the following 

 equation: 



H H H H 



HC/ ^N + CH, + O = Kcf S^/ 



H H H H 



(pyridine) 



This reaction is of special importance, because many alkaloids contam 

 a pyridine group; and the resulting methyl compound may be less 

 toxic than the original alkaloid — e. g., methyl morphine. 



6. Sulphur split off from proteins may combine with CNH and 

 CNK, converting them into the much less toxic sulphocyanides.^' 



7. Bile Acids. — All the above mentioned reactions are protective 

 largely because the substances formed are soluble and rapidly elim- 

 inated, as well as being less toxic than the original poison. Com- 

 pounds of many poisons are formed with bile acids which are insoluble, 

 and therefore only slowly dissolve or decompose, thus protecting the 

 body from overwhelming doses of the poison. Such compounds are 

 formed, not only with inorganic poisons, but also with alkaloids, espe- 

 cially strychnine, brucine, and quinine. They ar(^ then tlepositetl in 

 the livei', to be slowly dissolved and eliminated. 



((Occasionally acetic acid and cysteine have been observed to act as 

 combining substances. Calcium may be considered a defensive agent 

 against certain poisons [oxalic and citric acids] with. which it forms 

 insoluble* compounds, although it is probable that the toxicity of oxa- 

 lates depends largely upon their robbing the cells of calcium.''-) 



"' See Meuriee, Arch. int. I'liariiuicodyii., 1900 (7), 11. 



■"' See Robert son .•nil I Miniicl I, .lour. I'harniiicol., IIHL' (:>), «);5.'). 



