71 
CHAPTER XII. 
MUSCULAR SYSTEM. 
Size of Muscles — StrucHire — Contraction and Expajtsion — 
Muscle Corpuscles — Bundles of Muscular Fibres — Tendons — 
Muscles of Thorax a7id Jaiv — Power of Traction of Bee — 
Volu7itary and Involuntary Muscular Actio^i. 
The bee has a very powerful muscular system, by 
which every movement is accomplished. The muscles 
vary greatly in size, and some are made up of bundles 
of fibres, whilst others may consist of only a single 
fibre. They are actuated by the nerves, which cause 
them to contract or expand. 
If examined under the microscope, they appear 
transversely striped (Fig. 33), 
transparent, homogeneous, elastic 
outer membrane, the sarcolemtna^ 
and dark delicate lines stretching 
across the fibre at regular inter- 
vals, so as to sub-divide the space 
within the sarcolemma into uni- 
form transverse compartments, 
or discs. These membranes, 
Klein ( 79 ) says, appear fixed 
to the sarcolemma, so that if the muscle is stretched 
or contracted its surface is not smooth, but regularly 
and transversely undulating (Fig. 33, b). 
Each fibre during contraction becomes shorter and 
thicker (Fig. 33, b, h). In the living, uninjured muscular 
fibres, a contraction starts at one point and passes over 
and consist of a 
Fig* 33* — Muscles. 
