Sibyl T. Jewson and F. Tattbrsfield 



229 



From a qualitative point of view Pyridine seems to have an entirely 

 characteristic reaction. In the case of Aniline the survivors up to the 

 50 per cent, death point are fairly active. With Pyridine, however, from 

 the smallest dose upwards the survivors are obviously seriously incapaci- 

 tated; they appear to be suffering from motor paralysis and are only 

 just capable of twitching mouth parts and legs. This unfortunately can- 

 not be expressed graphically, but the condition is so marked as to indicate 

 that Pyridine has a very powerful and possibly a specific toxic action on 

 these pests. So small a concentration as -0017 c.c. in 1000 c.c. of air is 



40 80 120 



Millionths of gm. molecule per 1000 c.c. 

 X X Pyridine. O O Aniline. Air saturated at close of experiment. 



Fig. 2. Toxic effect on mites of inerep iing concentrations of the vapours of 

 Pyridine and Aniline. 



capable of almost completely paralysing in three hours nearly 100 per 

 cent, of the mites. 



8. Toxic Effect of Pyridine on Fungi, 



After prehminary trials had shown that Pyridine was successful in 

 ehminating mites a large number of infected cultures were treated with 

 the vapour of Pyridine overnight (16 hours). The infection consisted 

 chiefly of A.farinae with a large number of eggs, some T. longior while 

 several cultures of Mucor were also infected with G. sjnnipes or G. cada- 

 verum. The cultures were examined a week after treatment and there 



