160 CHEMICAL MEANS OF DEFENSE AGAINST POISONS 



organs ; also by forming sulphides with the H 2 S of the intes- 

 tinal contents. According to Cloetta 1 immunization against 

 arsenic depends entirely upon a reduction of absorption in the 

 intestine, for the longer arsenic is taken, the less appears in the 

 urine and the more appears in the feces. At the same time the 

 resistance to arsenic injected subcutaneously is not increased at 

 all, and no increase in resistance can be obtained by repeated 

 subcutaneous injections of sublethal doses. 



Free acids and alkalies are partly neutralized by the alkaline 

 and acid contents of the gastro-intestinal tract, partly by form- 

 ing compounds with the proteids, and partly by the alkalies and 

 carbonic acid of the blood stream. (See " Acid Intoxication," 

 Chap, xviii.) Phosphorus and sulphides are oxidized after 

 absorption into phosphoric and sulphuric acid, which are in 

 turn neutralized by the alkalinity of the blood and tissues. 

 Lillie 2 has called attention to the close, palisade arrangement 

 of the nuclei of the epithelium lining the alimentary tract, which 

 makes it necessary for all substances absorbed to pass through the 

 zone of their active oxidative influence, a fact undoubtedly of 

 great importance in the defense of the body. 



Reduction of iodic acid, chloric acid, hypochlorous acid, and 

 their salts occurs in the body, resulting in their conversion into 

 the much less toxic iodides and chlorides. Tellurium com- 

 pounds are also reduced and rendered insoluble. This reaction 

 occurs to some extent in the intestines ; how much in other 

 organs is unknown. 



Methylation, the addition of CH 3 groups, is observed in 

 poisoning by tellurium, which is eliminated in the breath as 

 methyl telluride, and also in the sweat and feces. 3 Selenium, 

 pyridine, and some other substances also combine with methane. 

 The source of the methane is possibly in the xanthin molecule. 



Summary. There are, therefore, three chief reactions used 

 against inorganic poisons in the body, oxidation, reduction, and 

 splitting off of water ; neutralization of acids or alkalies and the 

 formation of albuminates and sulphides being included under 

 the last heading, since in these reactions the splitting oifof 

 water is an essential step. 



ORGANIC POISONS 



In the case of organic poisons an equally small number of 

 primary reactions is employed in their detoxication, but in 



1 Arch. exp. Path. u. Pharm., 1906 (54), 196. 



2 Amer. Jour. Physiol., 1902 (7), 412. 



3 See Mead and Gies, Amer. Jour. Physiol., 1901 (5), 105. 



