48 
the hand, and to play an important part by its locomotive powers 
in its cell, and in the effect on the tissues caused thereby. The 
visceral contents are now thick, and obviously formed of the filthy 
matter which is caused by the perpetual irritation of the suction of 
the mouth-end of the maggot at the bottom of the sac. It is also 
now furnished with a small curved caudal aperture, placed nearly 
between the spiracles, from which some slight amount of discharge 
of contents can take place. 
The accompanying figure, in which the maggot is represented 
as in its natural position (tail end uppermost), shows it about four 
times the natural size in its fully-developed 
state, with the tips of the pair of spiracles in¬ 
dicated in the centre of the tail-end. It is, as 
is well-known, when full-fed, and for much of 
its previous life, of a bluntly oval somewhat 
compressed shape, of various shades of colour, 
from whitish to deep grey or brownish, and 
marked with cross-bands, which, under the 
magnifier, are seen to be formed (as figured 
at p. 47) of minute prickles. 
The above are the main differences connected 
ivith successive moults up to the fully-developed 
M magnified Ch f° rm °f the maggot, or larva; and following 
on these alterations in its structure, and 
especially on the power of keeping up a constant irritation by 
means of the muscular expansion and contraction of its prickly 
skin, we find the lining membrane of the cell increasing in thick¬ 
ness until it becomes well defined as a tough wall round the per¬ 
foration, or warble-hole, continuous with the upper part of the cell. 
The figure shows a warble-cell, drawn 
in section, after soaking in water, so 
that it is slightly magnified, and the 
lining membrane, or kind of false skin, 
which has formed round the warble- 
hole, and which runs partly down into 
the cell below, is clearly observable. 
At this stage, as long as the host 
animal is alive, the warble is noticeable 
amongst the hair of the hide as a good-sized lump, with an opening- 
in the middle, in which the tail of the maggot, with its two large 
dark breathing-pores, is visible. When the hide is removed, as the 
pressure from beneath ceases, the maggot is instead much more to be 
Section of warble-cell, after 
soaking in water. 
