Sibyl T. Jewson and F. Tattersfield 



225 



Table V {contd.) 



Vapour of pure Pyridine. Examination after 16 hours. 



% calculated on live 

 mites in control 



Time of 

 Exposure 



Controls 



A. 7-5 mins. 



B. 15 



C. 22-5 „ 



D. 30 



E. 37-5 „ 



F. 45 



G. 52-5 „ 

 H. 60 



I. 67-5 „ 

 J. 75 



K. 82-5 „ 

 L. 90 



No. 

 Alive 



(50 

 40 



(50 5) 



140 5) 



|89 

 132 

 130 



(81 



l83 



(83 



[85 



45 



45 



3 



7 



6 



6 







No. 

 Dead 



5 



18 

 11 

 13 

 22 



32] 

 17f 

 17| 

 15) 

 65 

 55 

 97 

 98 

 94 

 94 

 100 



Alive 

 90 



85-8 



91 



85-5 



77 



84 



45 

 45 



3 



6-6 



6 



6 







9/ 

 /o 



Dead 

 10 



14-2 



9 

 14-5 



23 



16 



55 

 55 



97 

 93-4 

 94 

 94 

 100 



/o 

 Alive 



100 



95 



100 

 95 



85-5 



93 



50 



50 

 3 



7 



. 7 



7 







/o 

 Dead 





 5 



14-5 



50 

 50 

 97 

 93 

 93 

 93 

 100 



Vapour of pure Aniline. Examination immediately after treatment. 



Control 



A. 60 rains. 



B. 120 „ 



C. 180 „ 



D. 240 „ 



E. 300 „ 



86 



81 



43 



5 



2 



1 



14 



19 

 57 

 95 

 98 

 99 



86 

 81 

 43 



14 

 19 

 57 

 95 

 98 

 99 



100 



94 



50 



6 



2 



1 



6 

 50 

 94 

 98 

 99 



which time the vapour had escaped. An inspection of Table V and 

 Fig. la shows that immediate examination rather understates the effect 

 of the poison. The proportion of live to dead mites was counted in both 

 treated tubes and controls and the percentage of survivors in the tests 

 to the live mites in the controls calculated. This percentage was plotted 

 against time. The results are set out in Table V and Fig. 1 a. 



Fig. la shows that air saturated with Pyridine is rather more toxic 

 than when saturated with Aniline. This does not mean that weight for 

 weight or molecule for molecule Pyridine is more toxic than Anihne; as 

 the latter having a lower vapour pressure at ordinary temperatures 

 (15°-18° C.) would saturate air with less of that material (weight for 

 weight) in the vapour phase. The curves take the usual sigmoid form 

 characteristic of such reactions. Henderson Smith (4) who studied the 

 toxic action of Phenol on Botrytis spores obtained curves of a similar 



Ann. BioL ix 15 



