3 o6 
second pair, there is a pore, from which the secretion 
of the large coxal gland, described later, is at times 
exuded. 
(2) Argas .—Note the pit-like structures on the 
dorsum and also the absence of the fold around the 
base of the rostrum. 
Internal Anatomy and Dissection of Ticks 
(A) Ornithodoros 
1. With a sharp pair of scissors snip all round the 
edge so that the dorsal and ventral surfaces of the tick 
are completely separated. 
2. Place the tick in a dissecting trough* in salt 
solution, and fix the ventral chitin by means of fine 
pins or hedgehog quills. Remove the dorsal piece by 
grasping it behind with a pair of forceps and dragging 
it forwards over the head, detaching any structures 
which may adhere to it with a touch or two of a needle. 
3. Whilst carefully removing tracheal tissue and 
separating the organs observe, in the female, a thin 
sheet of tissue stretched over the whole dorsum. This 
is composed of fat tissue and tracheal branches. 
Heart .—In the central line is the tubular heart 
dilated, at about the junction of the posterior with the 
middle third of the body to form a conspicuous sac. 
Alimentary Diverticula .—Note that there is a 
central short median ventricle or sac receiving anteriorly 
the oesophagus and ending posteriorly in the fine, almost 
capillary, tube which passes to the rectum. Trace out 
a number of anterior, lateral and posterior blind 
* A dissecting trough can be purchased, or readily made in the following way. 
Put some pieces of lead at the bottom of a convenient dish and pour over them a 
mixture of melted paraffin wax (melting point about 6o° C.) and soot or fine animal 
charcoal. 
