HELIX — MUSCULAR SYSTEM. 
159 
but interesting character, may be mentioned the extrinsic and 
intrinsic muscles of the buccal bulb. 
The muscles or cartilages here especially alluded to, are of a pearly 
glistening white and very strong and ribbon-like in character. 
The columellar muscle, by which the animal is organically attached 
to the shell, is the largest and most important muscle of the body, 
and is affixed at its distal end to the columella near the commence- 
ment of the penultimate whorl (see p. 54, f 130) and passes beneath 
the lung chamber, along the inner or right side of the spiral, 
dividing to the right and left into numerous fibres which interlace 
with the tissues of the foot. 
Near its origin the columellar muscle gives rise to the paired 
tentacular retractors, each of which, prior to entering the tentacles 
and before re-bifurcation, gives off a broad tripartite muscle to the 
anterior part of the foot ; the retractor of the dorsal tentacle expands 
noticeably before reaching the apex, while that to the lower tentacle 
again divides, sending a strong branch to the lip. 
The pharyngeal or buccal retractor originates adjoining to and im- 
mediately in advance of the paired tentacidar muscles and is formed 
by a powerful ribbon-like muscle, 
which divides before reaching the 
buccal bulb, to which it is attached 
ventrally and laterally by the ex- 
panded ends. 
The Penial retractor is a powerful 
unpaired muscle attached to the distal 
end of the penis sheath and to the 
floor of the pulmonary chamber. 
The extrinsic muscles of the buccal 
bulb are formed by the pharyngeal 
retractor and by a number of slender 
muscular bands, which pass from its 
exterior to the walls of the anterior region of the body, and in 
accordance with their function are distinguished as depressor, levator 
or protractor muscles. 
The intrinsic muscles are formed chiefly by the protractor and 
retractor fibres, attached to the radular cartilage anteriorly and 
])osteriorly respectively, and communicating the motion to the 
radular membrane. 
F IG. 322. — Cephalic retractors of Helix 
aspersa X 4. 
c.m. columellar muscle; j. anterior 
foot retractors ; pharyngeal or buccal 
retractor ; /. tentacular retractors. 
