242 LIFE: ITS NATURE AND ORIGIN 



drugs, 54 led D. D. Woods 55 to the widely accepted view that the two 

 substances compete for a bacterial enzyme system which uses PABA 

 as an essential metabolite. But R. J. Henry 56 believes that 

 PABA excludes the sulfa drug from some enzyme, probably the 

 dehydrogenases or the protein co-enzymase systems. 



The well-known ability of many pathogenic organisms to develop 

 resistance to sulfa drugs, streptomycin, etc., indicates that they can 

 form specific antibodies, or else develop catalysts which can destroy 

 the drugs, or can become incapable of combining with the drugs, 

 either by physicochemical change or by the formation of a pro- 

 tective layer. 57 



One of the most feared "poison gases" of World War I was lewisite 

 (CI — CH=CHAsCl 2 ), which poisons various catalysts. Peters, Stocken 

 and Thompson 58 reported that dimercaptopropanol 



OH SH SH 



1 I J, 



C — C — C 



I I I 



H 2 H H 2 



known as BAL (British anti-lewisite) serves as an antidote. Among 

 other things, it stops the toxic action of lewisite on the pyruvate oxi- 

 dase system of the brain; and its selective affinity for arsenic and 

 heavy metals enables it to reverse or detoxify the inhibition of SH 

 enzymes by other metals. It has been used successfully against arsenic 

 poisoning after intensive arsenical therapy for syphilis, and also in 

 corrosive sublimate poisoning (HgCl 2 ), and in brass founders' fever 

 (Zn). "BAL in oil for intramuscular injection should be stocked in 

 every hospital pharmacy" (Leonard). 



In World War II, a much feared but unused "gas" was di-isopropyl 

 fluorophosphate (DFP), which irreversibly inhibits cholinesterase, the 

 enzyme (or rather, group of like enzymes) that plays an essential role 

 in muscular contraction and in the transmission of nerve impulses. 

 There is evidence that rabbit and human plasma, blood cells, and 

 tissues contain an enzyme capable of hydrolyzing the fluorophosphate, 

 and much of this enzyme is contained in the liver. It may be seen 

 that the degree of physiological symptoms or the death of the animal 

 is a resultant of the two processes. The present data do not permit 

 a quantitative evaluation of the role of each of these processes. 59 



Fluoroacetate of sodium, recently introduced as a rodenticide, kills 

 many mammals, the results varying with the species; most commonly 

 ventricular fibrillation or excessive stimulation of the central nervous 

 system causes death. 60 The plant Dichapetalum cymosum, known to 

 South African farmers as "Gifblaar" is reported by J. S. C. Marais to 

 contain monofluoroacetic acid, and 1.0 to 1.5 grams per kilo of the 

 dried plant is lethal for rabbits. 61 The "nitrogen mustards'* (bis and 



