164 CHEMICAL MEANS OF DEFENSE AGAINST POISOXS 



7. Bile Acids. All the above-mentioned reactions are pro- 

 tective largely because the substances formed are soluble and 

 rapidly eliminated, as well as being less toxic than the original 

 poison. Compounds 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, especially strychnin, 

 brucin, and quinin. They are then deposited in the liver, to be 

 slowly dissolved and eliminated. 



Occasionally acetic acid and cystein have been observed to 

 act as combining substances. 



Neutralization of organic acids entering the body or formed 

 in metabolism is accomplished by the sodium carbonate of the 

 blood when 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. 1 (See " Acid Intoxication," Chap. 

 xviii.) 



Dehydration, which plays a prominent part in a number 

 of the above-mentioned syntheses, is particularly important in 

 the change of ammonium carbonate into urea : 



4 (X 2V 



\CO == >CO + 2H 2 0. 

 4 <y 



As ammonium salts of all sorts are very toxic, especially hemo- 

 lytic, while 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 that is 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 number. The reactions are : oxidation and reduction, 

 hydration and dehydration, and perhaps simple addition (methyl- 

 ation). The chief known protective substances are the alkalies 

 of the blood, proteids, hydrogen sulphide, sulphuric acid, glyco- 

 coll, urea, cystein, bile acids, glycuronic acid, and acetic acid. 

 All these substances are normally present in the body, and none 

 of them is specific against any one poison, but each combines 

 with several poisons. This last fact is interesting in comparison 



1 In this connection it may be mentioned that the bactericidal power of the 

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

 than usual. 



