226 
Culicifuges 
Many culicifuges lack efficiency owing to unsuitable preparation rather 
than to defects in their essential constituents. There is a general tendency on 
the part of makers to use too heavy a percentage of some inert base. Though 
in the case of a wax this may be useful in raising the melting point and in 
retarding volatilization, it must be condemned where the result is to diminish 
the effectiveness of the preparations. For instance, preparations 3, 4, 5 and 
22 would doubtless give better results if compounded with less base and 
rendered easier to spread on the skin. 
An ideal culicifuge should (1) spread easily so as to enable it to be quickly 
and evenly applied over the exposed area, while (2) at the same time it must 
be of such a consistency that it will adhere firmly to the skin, and (3) retard 
volatilization. In respect of points 1 and 3, preparations need modification 
according to their intended use in tropical or temperate climates. (See also 
notes following Table I.) 
The individual likes of people in regard to odours are varied and their 
dislikes so intense in some cases as to amount almost to physical discomfort, 
with the result that irritation caused by the bites would be preferred to the 
use of an objectionable culicifuge; some people greatly preferring the heavy 
odours of spices or gums to the cleaner if more penetrating smells of such 
substances as naphthalene and tarry or wood distillates. 
These considerations make it hard to advise as to the best of a number of 
preparations giving approximately equal degrees of protection. Among troops 
and others compulsorily subjected to measures of malaria control, a prepara¬ 
tion, the odour of which is greatly disliked, might fail because the majority 
would not apply it, or do so indifferently. The difficulty might be successfully 
met by adopting two classes of preparations. 
The question of cost is also of importance; where large quantities are 
needed such preparations as 15 a, 9 6, and 21 would easily outclass equally 
serviceable ones depending upon costly essential oils for their efficiency. 
VII. METHODS ADOPTED FOR TESTING PREPARATIONS. 
The two cages used for carrying out the tests were similar to those 
employed for experimenting with this mosquito in West Africa under the 
auspices of the Yellow Fever Commission. The framework is of wood screwed 
together, the top and sides being of wire gauze with a circular hole 5 inches 
in diameter cut in one side to which is fastened a sleeve of mosquito netting. 
These cages measure on the inside 1 foot 6 inches in height, 2 feet in length, 
1 foot 3J inches in breadth. They are fully described and illustrated in the 
Reports of the Yellow Fever Commission , vol. hi, pp. 169-172, 1916. 
Each cage was used only once in 3 or 4 days, as the mosquitoes’ desire 
for blood normally recurs at about 3-4 days intervals. On the occasions of the 
tests the mosquitoes were therefore ravenous. 
The method adopted in testing a preparation was as follows: 
