E. Hindle and Gt. Merriman 
215 
expei’iments the following procedure was found to be the most satis¬ 
factory :— 
A piece of glass tube about 3 inches in length and 1 inch in diameter 
was closed at one end by a piece of diaphragm from a freshly killed rat. 
This membrane was found to be the most suitable as it is of convenient 
strength and thickness to allow the tick to anchor itself for purposes of 
feeding. The tube was then completely filled with the liquid on which 
the ticks were required to feed and the open end closed by means of 
plasticine, care being taken to exclude any air bubbles. By means of 
its plasticine base, the tube was fixed vertically to the bottom of a 
saucepan, which was then filled with water to within about below 
the level of the membrane closing the upper end of the tube. The 
whole was then heated to about 4<2° C. and kept constant at this 
temperature. Ticks from which Haller’s organ had been removed, 
were now placed on the membrane and allowed to anchor themselves, 
which was usually accomplished without much hesitation, and the ticks 
then proceeded to gorge themselves on the fluid contained in the tube. 
In the first case a mixture of a trace of rat’s blood in sodium citrate 
solution was employed; the ticks having fully gorged on this almost 
transparent liquid presented a very curious translucent appearance. 
These ticks, however, did not emit any coxal fluid and were found dead 
the following day. In a second case, liquid gelatin was employed 
which was also ingested though less readily than the previous liquid. 
Ticks were also fed on normal 0'8 “/o NaCl solution without the addition 
of any other substance. 
Having obtained these results with Argas persicm, we went on to 
experiment with other species of ticks, from which Haller’s organs had 
been removed. Ornitliodorus moubata behaved in exactly a similar 
manner to Argas loersicus, and fed on liquid gelatin. On the other hand, 
it was found that Hyalomma aegyptium although they attempted to 
anchor themselves were unable to do so owing to the slippery nature of 
the membrane. Accordingly a piece of ordinary rat skin with the hair 
outside was used instead of the diaphragm and it was then found that 
the ticks readily anchored themselves and commenced to feed on the 
normal salt solution contained in the tube. 
These experiments demonstrate that in the absence of Haller’s 
organs a tick loses all power of discriminating its host. In finding a 
host the tick seems to be mainly governed by two factors. First, the 
effect of heat, the perception of which is (listributed over the general 
surface of the body, and secondly the sense of smell, located in Haller’s 
