Biological Papers. 



139 



substances. For example, stating the quantity of sulphur dioxide 

 necessary to kill the bedbug as 8, we have the quantity of formal- 

 dehyde (4:0 per cent solution) necessary to produce the same effect 

 as 54 plus, making the calculated coefficient of sulphur dioxide, 



Apparatus used by McClintock, Hamilton, and Lowe. 



for this insect, as 1, and that of formaldehyde 0.1 The authors 

 have tabulated in their report the coefficients of thirty-eight differ- 

 ent insecticides, including such articles as the above mentioned, 

 and, in addition, creosote, carbolic acid, naphthalene, kerosene, oil 



