The Anatomy of Ants. By Sir John Lubbock, Bart. 139 
head are those which move the mandibles, and of them the flexors 
are more powerful than the elevators or extensors. In fact, they 
occupy a large part of the upper and hinder portion of the head. 
The fibres are attached separately to the wall of the head, and form 
two principal groups, which, however, are attached to a single 
tendon, running to the inner angle of the base of the mandible. 
They are shown in Plate CXC., Figs. 1 and 2, nut 1. The spaces 
between the groups of fibres constituting this muscle are occupied 
by tracheal sacs. Some of the cut ends of these muscles are 
also shown in Plate CLXXXIX., Figs. 2 and 3. The elevators 
(Plate CXC., Fig. 3, md 3) are attached to the upper side of the 
head, and pass downwards and forwards to the inner angle of the 
mandibles. 
The extensor muscles (Plate CXC., Fig. 1, md 2) are much less 
powerful. They rise by several separate fibres along the central 
neural ridge, and passing forwards and outwards are attached to 
the external angle of the mandible. 
The muscles of the maxillae, though less powerful, are more 
complex than those of the mandibles. The principal ones are 
shown in Plate CLXXXIX., Fig. 1, mx 1 and mx 2. Plate 
CXCII., Fig. 7, shows the base of the maxilla with the hinge, or 
cardo. The organ is thrown outwards by the muscle shown in 
Plate CLXXXIX., Fig. 1, mx 1, while, on the other hand, it is 
retracted by the muscle (Plate CLXXXIX., Fig. 1, mx 2) which 
is attached to the antero-posterior process. The bases of the 
maxillae and labium being firmly attached together, the muscles 
which move that portion of the labium affect the maxillae also. 
The muscles which move the maxillae necessarily also affect the 
labium. The labium has, however, also special muscles of its own. 
Plate CLXXXIX., Fig. 1, L 1, L 2, and L 3 ; Plate CLXXXIX., 
Fig. 3, L 1 and L 2. 
In the posterior wall of the mouth is an orifice which leads into 
a large globular sac (Plate CLXXXIX., Fig. 1, Plate CLXXXIX., 
Fig. 3, m) which was, I believe, first observed by Brants, and to 
which he gave the name of “ Lijmholte.” Its membranous walls 
appear to be firm and elastic. I have not found any muscles 
attached to it, and presume that it is kept open by the elasticity 
of the walls. The orifice of the mouth sac can be closed at will 
by a small flap (Plate CLXXXIX., Fig. 3, fl), which is supplied 
with several muscular fascicles (Plate CLXXXIX., Fig. 3, MM). 
The cavity generally contains a brown, spongy mass, in which I 
once (in a specimen of Formica rufa ) found a small hematoid 
worm. Brants is of opinion that the mouth sac is emptied by 
the action of the muscles which retract the proboscis, while the 
lingualis (i in Brants’ fig. 11) as he supposes, by raising the 
hypopharynx, opens the cavity. His account does not seem to 
