210 
Sensory Perceptions in Tielzs 
Olfactory sense. 
Lahille is the only writer who has hitherto published any definite 
experiments relating to this subject. He found that when barriers of 
a solution of “ Sarnol ” of either 1 ®/o or 100 % ''^ere placed across the 
track of a moving Boophilus ( $ )—the only tick with which he experi¬ 
mented—the parasite turned aside before having actually touched the 
liquid. On the other hand, ticks which had suffered amputation of the 
first pair of legs, thus being deprived of their Haller’s organs, were not 
checked in their paths by barriers of 1 “/o Sarnol, but hesitated slightly 
before crossing barriers of pure Sarnol. From these experiments 
Lahille concluded that ticks possess an olfactory sense residing in Haller’s 
organ, and that in addition the whole body is sensitive to very strong 
odours such as pure Sarnol. Miss Jordan Lloyd performed various 
experiments wuth gorged nymphs of Rhipicephalns bursa which seemed 
to confirm Lahille’s results. In addition to amputation of the Haller’s 
organs, she also employed the method of occluding them by means of 
a solution of Canada Balsam in benzol. Although the experiments with 
R. bursa seemed to demonstrate the existence of an olfactory sense in 
these ticks, the results obtained with Argas persicus were very 
indefinite. 
Our experiments on the sense of smell have been made almost en¬ 
tirely on Ai'gas persicus, and at first we employed the method of placing 
barriers of various odoriferous substances across the paths of moving 
ticks. Later this method was abandoned as it also brought in various 
conflicting factors, such as touch, heat etc., which interfered with a true 
interpretation of the results. The method we finally adopted was to 
employ merely the vapours of various odoriferous substances in the 
manner which will be described below. 
I. Experiments with normal ticks. 
In the first case are given the results obtained by the use of 
barriers of various odoriferous liquids and solids. In each case control 
experiments were made by placing barriers of either w^ater or sand 
across the paths of moving ticks in order to determine whether they 
were affected by the sense of touch. The method adopted in each 
experiment was as follows :— 
A definite number of ticks, usually nymphs and adults, were 
placed in the middle of a large sheet of filter paper, arranged in front of 
