No. 3.] MUSCLES AND NERVES [IN AMIA CALVA. Sys 
cess, from the entire outer surface of that process, and also by 
a few fibres from the outer surface of the metapterygoid mem- 
brane, some of the outermost of these last fibres overlapping the 
membrane and arising from the outer surface of the hyoman- 
dibular beyond it. A; is continuous below, or ventrally, with 
A2',as already described. Its fibres converge strongly and are 
all inserted on a broad tendon or fascia, 4; Aw", formed where 
the muscle passes into the ramus of the mandible. 
The mandibular portion of the adductor, Aw, is that part of 
the muscle that lies inside the hollow of the ramus of the man- 
dible. It can be separated into two parts, Aw! and Aw", which 
are distinct and separate in origin and insertion. There is, 
however, no smooth and even surface of separation between 
these two parts, as there is between Az and 43. On the con- 
trary, the surfaces are rough and uneven, muscle fibres, or 
bundles of one division, projecting into and interlocking with 
those of the other, so that they must be carefully pulled apart 
to effect a separation of the muscles. There is, however, no 
interchange of fibres between the two divisions, each being 
confined strictly to its own region of origin and insertion. 
The larger, outer portion, Ao’, has its origin from the broad 
tendon Az Aw’. Its fibres arise from the outer surface of the 
tendon, near the hind end of the mandible, and pass directly, 
with the outer fibres of A2”, to their common insertion on the 
entire inner surface of the dentary and the anterior part of the 
angular. The arrangement is such as would arise if a single 
broad muscle, arising at or near the preoperculum and having 
its insertion inside the ramus of the mandible, thus represent- 
ing Aw! and the greater part of Az, should become contracted, 
and in part tendinous, near the middle of its length. 
The inner, deeper portion, A", of the mandibular muscle is 
much smaller than the outer one. It arises entirely from the 
tendon or fascia formed on the outer surface of A 3, and is inserted, 
as a flat, thin muscle, along the upper surface of the posterior half 
of the longitudinal cartilaginous rib which, as described by van 
Wijhe (No. 129, p. 281), projects horizontally from the lower 
edge of Meckel’s cartilage into the hollow of the ramus of the 
mandible. Considered together with 4, it forms in outline, on 
