auerbach: effects of chemicals 125 



that the active principle in the production of lung tumors by 

 urethane is a metabolite which is produced in mice but not in 

 guinea-pigs. It is, therefore, possible that Neurospora is resistant 

 to the mutagenic action of urethane because it cannot form the 

 mutagenically effective metabolite. Oehlkers attributes the chro- 

 mosome-breaking action of urethane in plant cells to general dis- 

 turbances of metabolism. Rogers (78) has shown a close connec- 

 tion between urethane and nucleic acid metabolism. In Droso- 

 phila breaks produced by urethane and X-rays interact freely with 

 each other to give the number of rearrangements expected from 

 the overall number of breaks by both treatments (73). 



Alkaloids 



Oehlkers and his collaborators (72) have found that a num- 

 ber of pharmacologically important alkaloids, such as morphine 

 and scopolamine, produce chromosome rearrangements in plants. 

 Quite recently, Clark in Australia (20) has established that certain 

 alkaloids, e.g., heliotrin and related substances, are highly effec- 

 tive mutagens for Drosophila. These substances occur in Senecio 

 and some other plants and cause liver disease in sheep. 



Peroxides 



This group forms a link between chemical and radiation muta- 

 genesis, for peroxides have been shown to play the role of interme- 

 diates in mutagenesis by ultraviolet light and, probably, X-rays. 

 Hydrogen peroxide is a weak mutagen for micro-organisms (46), but 

 is wholly ineffective in Drosophila where it is quickly destroyed 

 by catalase. Certain organic peroxides, on the other hand, are effec- 

 tive mutagens for both Drosophila and Neurospora (3, 28, 82). 



Formaldehyde 



The mutagenic action of formaldehyde was discovered by 

 Rapoport (74) soon after the last war. He obtained high mutation 

 frequencies by mixing formaldehyde with the food of Drosophila 

 larvae. Mutations can also be produced by injecting aqueous solu- 

 tions of formaldehyde into the abdomen of adult flies (6). This is 

 a less effective method but will be discussed first because there are 

 reasons to believe that it acts via the formation of organic peroxides 

 from formaldehyde and metabolically produced hydrogen perox- 



