OROANIC POISONS 251 



6. Sulphur si)lit off from proteins may coml)ine with CNII and CNK. 

 oonvertinp: them into the much less toxic sulphocyanides.-"' 



7. Bile Acids. — All tlie above-mentioned reactions are protective 

 largely beeaiise the substances formed are solultie 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 overwlielming doses of the poison. Sncli eoiu])ounds are 

 fonned, not only with inorganic ])oisons, but also with alkaloids, espe- 

 cially strychnin, brucin, and (|uiiiin. They are then deposited in the 

 liver, to be slowly dissolved and eliminated. 



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

 <'ombining 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 dejiends largely upon their robbing the cells of calcium.-') 



Neutralization of organic acids entering the body or formed in 

 metabolism is accomplished by the sodium carbonate of the blood 

 W'hen in small amounts; if excessive in quantity (e. g., diabetic coma), 

 a portion is combined with ammonia and appears as an ammonium 

 salt in the urine. Magnesium and calcium salts may also help in the 

 neutralization, probably at the expense of the bone tissue.-^ (See 

 ^'Acid Intoxication," Chap, xviii.) 



Dehydration, wdiich plays a prominent part in a number of the 

 above-mentioned syntheses, is particularly important in the change 

 of ammonium carbonate into urea : 



XH,— NH„ 



"^('0 = ^CO + 2H2O. 

 XH,— XH„ 



As ammonium salts of all sorts are very toxic, especially hemolytic, 

 w^hile urea is not, this process is probably one of the most important 

 detoxicating reactions of the body because of the great amount of 

 ammonium compounds thaf^s constantly being formed in nitrogenous 

 metabolism. 



Summary. — As Fromm points out, the variety of reactions and the 

 variety of defensive substances are both remarkably small in num- 

 ber. The reactions are : oxidation and reduction, hydration and de- 

 hydration, and perhaps simple addition (methylation). The chief 

 known protective substances are the alkalies of the blood, proteins, 

 hydrogen sulphide, sulphuric acid, glycocoll, urea, cysteine, bile acids, 



2G See ;Nreurice, Arch. int. Pliarmaeodyn., IflOO (7), 11. 



27 See Robertson and Burnett, Jour. Pharmacol., 1012 (.3), 6.3.5. 



28 In this connection it may l)e mentionerl that the bactericidal power of the 

 blood is increased if the blood is more alkaline, decreased if it is less alkaline, 

 than usual. 



