W. F. COOPKR AM) W. II. NUTTALL 275 



pliysical coii.staiits shoukl behave in a similar iiiaiiiier. Unfortunately 

 there is no reliable information at hand to decide the point, invaluable 

 as such knowledge would be as a basis for research on these lines. 



Again, the efficiency of carboHc and cresylic acids as insecticides 

 is universally known, and it is reasonable to presume that these 

 compounds possess insecticidal properties by virtue of their phenolic 

 groups. Benzene compounds containing a nitro-group have germicidal 

 properties, and have been suggested as insecticides — as for example, 

 nitro-benzene. It is conceivable, therefore, that the nitro-group, like 

 the phenolic group, may confer insecticidal properties, if introduced into 

 a molecule. Would the insecticidal properties of carbolic or cresylic 

 acid, therefore, be increased by the introduction of one or more nitro- 

 groups? This was the question which the Bayer Farbenfabrik asked 

 themselves as early as 1892, and, as the result of systematic research, 

 they were able to answer it in the affirmative and produce a most 

 valuable insecticide, " Antinonnin." This is ortho-cresol into which 

 two nitro-groups have been introduced, the potassium salt of the result- 

 ing compound, owing to its greater solubility, being employed in practice. 

 It is non-corrosive, and attacks neither metals nor textile fabrics. 

 Antinonnin has been extensively and successfully applied in the 

 destruction of the "Nonnen" {Monacha) larvae, infesting the forests 

 of Bavaria and Wlirtemberg; and has also been largely used as a 

 substitute for creosote in the preservation of timber. This afTords an 

 excellent illustration of the value of systematic research as opposed to 

 empirical methods. 



The subject of insecticidal effect of the introduction of various 

 atomic groups into the molecule needs to be worked out systemati- 

 cally, much in the same manner as that in which Ehrlich carried out his 

 classic investigations on the effect of various organic arsenic compounds 

 on blood parasites. Ehrlich found that the position of the arsenic in 

 the molecule had an enormous influence on the toxic effect of the 

 compound, both on the host and the blood parasite; and, as a result 

 of a long and systematic research, he at length evolved his famous 

 " 606," efficacious doses of which, whilst highly toxic to blood parasites, 

 are practically innocuous to the host. 



Speaking generally, metals in organic combinations, as distinct from 

 inorganic, are considerably less toxic towards the higher animals and 

 plants, whilst they retain their poisonous action on the lower organisms. 

 This fact suggests the possibility of the use of organo-metallic com- 

 pounds as insecticides. The insecticidal properties of the metal might 



Ann. Biol, i 19 



