350 GROWTH OF PLANTS 



the destruction of the nerves, there is a widespread clumping effect on the 

 chromatin of the nuclei in all the body tissues. In the muscles, stained with 

 iron hematoxylin and erythrosin, the nuclei are clumped into rod-like, 

 oblong masses, and the cytoplasm is fenestrated. There is a loss of sharp 

 stainability of the striations. This makes one realize why there is a loss 

 of locomotor faculties. 



Isobutylundecyleneamide, the activator of Pyrin,* causes chromatolysis, 

 as opposed to clumping action of pyrethrum of the nuclei. This activator 

 shows the same effect on the muscles as pyrethrum, but does not alter the 

 stainability of the striations. 



Pyrin combines the effects of both pyrethrum and activator. The combi- 

 nation of these two agents (as in Pyrin) shows a histological picture that is 

 a summation of the effect of both. The interaction of these two types of 

 nuclear destruction is believed to be the basis of activation. 



The toxic agents in pyrethrum flowers are two esters called pyrethrin I 

 and pyrethrin II. The relative toxicity of pyrethrins I and II was a contro- 

 versial subject.^' ^' ^^' ^° The discrepancies of the findings of various investi- 

 gators might be due either to different susceptibilities in insects used or 

 differences in the physical state of the pyrethrins at the moment of applica- 

 tion. Experiments were designed to test this hypothesis. The comparative 

 toxicity of pyrethrum extracts varying in ratios of pyrethrins I and II was 

 determined on Aphis rumicis, using acetone and a miscible oil as solvents 

 for pyrethrins with water. When extracts high in pyrethrin I were com- 

 pared with those high in pyrethria II using acetone as a solvent, the former 

 extracts were considerably more toxic than the latter. When a miscible 

 oil such as Penetrol was used as a solvent, the difference in toxicity tended 

 to disappear.-^ 



When similar extracts were tested on houseflies {Musca domestica L.) by 

 both the Peet-Grady and the modified Nelson methods the differences in 

 toxicity of the extracts high in pyrethrin I and those high in pyrethrin II 

 were not statistically significant. 



The results indicated that the physical condition of the pyrethrins at 

 the time of application is a determining factor in the relative toxicity, at 

 least so far as Aphis rumicis and Musca domestica are concerned. The 

 relative toxicity of pyrethrins I and II depends almost entirely on the 

 method of application. 



An improvement in the method of the determination of pyrethrin I was 

 made by Wilcoxon.^^ The reaction of chrysanthemum monocarboxylic 

 acid with Deniges' reagent was adapted to the quantitative determination 

 of pyrethrin I in pyrethrum flowers and extract. With slight modification 

 this has been adopted as the official method for the determination of pyreth- 

 rin I by the Association of Official Agricultural Chemists.^- ^' ^^ 



Various esters of chrysanthemum monocarboxylic acid were prepared by 

 Harvill.2^ 'pj^g lauryl, myristyl, cetyl, and diethanolamine esters at a con- 



* A product of John Powell & Company, Inc., New York, N. Y. 



