L. E. Robinson and J. Davidson 
219 
necessary as such dissections may be, they should always be checked 
and amplified by the study of serial sections of the entire tick, cut in 
the sagittal, transverse and horizontal planes, respectively. 
For the fixation of ticks before section-cutting, we have found 
Carnoy’s Glacial Acetic acid—Absolute alcohol—-Chloroform Mixture, 
in the proportions 1:C:3 very satisfactory. In addition, Flemming’s 
Fluid (strong formula) has given good results. For the demonstration 
of the secretion-granules in the salivary glands, Kopfsch’s Mixture gives 
striking results, but is not a desirable reagent for general use. In 
addition to the foregoing, we have used Kleinenberg’s Picro-sulphuric 
acid Mixture, Perenyi’s Fluid and Sublimate-acetic (10“/o acetic acid 
saturated with HgCk). Reference to the use of the first mixture has 
been made in Part I of this paper (p. 24) and the other two reagents 
do not give satisfactory results. There is reason to believe that Gilson’s 
Mixture—a modification of Carnoy’s Fluid, with the addition of mercuric 
chloride—is an eminently suitable fixative, but the authors have had no 
personal experience of this. 
As already pointed out, the thick chitinous cuticle of the tick is not 
readily permeated by fluids, and this makes fi.xation a less simple 
operation than usual. The mere immersion of the tick in the fixing fluid 
is not suflficient; and as mentioned above, incisions of the cuticle, made 
to assist penetration, lead to displacement of the organs. The most 
satisfactory method is to inject the fixative into the body by means of a 
hypodermic syringe. We used an “all-glass aseptic” syringe made by 
Messrs Burroughs Wellcome and Co., as being less subject to any cor¬ 
rosive action of the fixing fluids; the steel needle was protected by 
being dipped into hot melted vaseline and then drained, so as to leave 
a scarcely perceptible film of vaseline on the surface. The needles, as 
supplied, are too long in the orifice and it was found necessary to modify 
this defect by rubbing down the points to a more oblique angle. With 
care, a sharp cutting-edge may be maintained at the tip of the needle 
and no difficulty is experienced in penetrating the cuticle of the tick. 
The operation is carried out as follows :—the living tick is taken between 
the thumb and forefinger of the left hand, and the needle of the syringe, 
previously filled with the fixing reagent, is inserted transversely into the 
body, some little distance posterior to the anus, and as soon as the orifice 
in the needle is completely introduced, the fluid is slowly injected. In 
performing this operation, a sheet of glass should be interposed before 
the face of the operator to protect him from any accidental spurt of 
fixing fluid. As injection proceeds, the legs of the tick become stiffly 
15—2 
