104 . ELEVENTH REPORT. 



STANDARDIZATION OF CONTACT INSECTICIDES. 



E. M. Houghton H. C. Hamilton. 

 (From the Research.' Laboratory of Parke, Davis & Co.) 



..At first thought there may not seem to be a very close connection l^etween 

 the subject of this paper and the section before which it is read; but, since 

 Sanitary Science concerns itself with anything which affects the health of 

 the community, what is more interesting and vital than the agencies which 

 tend to cause and to spread disease? 



Outbreaks of infectious and contagious diseases have therefore, been 

 most carefully studied to learn the life history of the organism concerned. 

 As a result of these studies, it was discovered that in spreading disease 

 insects play a most important role. The direct or indirect connection of 

 flies with the spread of typhoid fever, mosciuitoes with malaria and yellow 

 fever, fleas on rats with bubonic plague, southern cattle ticks with the splenetic 

 or Texas fever of cattle, and a number of other cases just as interesting have 

 been proven beyond a doubt. The necessity for an accurate means of 

 standardizing insecticides is, therefore, clearly apparent. 



"Contact Insecticides" is a term used to denote such preparations as are 

 more or less effective when applied externally to insects, but which are 

 relatively non-toxic. Their non-toxicity is evidenced by the fact that, 

 when applied to the leaves of plants or to the skin of animals, insects are 

 not injured by feeding thereon, as is the case when arsenic is used. 



The particular insecticides to be considered are those of which creosote 

 oil is the effective ingredient and which are permitted by the Department 

 of Agriculture for use in curing sheep scab. Of necessity, when the U. S. 

 Government assumes the responsibility of approving the use of a product 

 which is to be purchased, certain restrictions must be placed on its manu- 

 facture to insure the use of proper material and uniformity in composition. 

 This is what is meant by "Standardization." 



Standardization in general is accomplished in a variety of ways; for example, 

 lime and sulphur solution should be adjusted to a definite standard by 

 determining the amount of sulphur as soluble sulphide and directing such a 

 dilution as will contain a definite quantity in this form. Arsenic compounds 

 should be assayed to determine not only the arsenic present, but the form 

 in which it appears, since the soluble form is injurious to the host, both to 

 animals and plants. 



Certain very valuable medicinal substances are of such a nature that their 

 efficiency can be determined only by a pharmacological assay; that is, to 

 determine how much must be administered to an animal to neutralize some 

 antagonistic substance or to produce a certain definite effect. In the latter 

 case, comparison is made with the standard, w^iich is a similar preparation 

 from the same drug and known to be of average activity. Such a method 

 of assay as that last described is applied for one to the other of three reasons: 



The constituents to which the drug owes its value may not have been 

 isolated; 



The constituents may be well known, but of such a nature as to make a 

 quantitative chemical assay difficult even if possible; 



