THE MUSCLES. 



CHAPTEK III. 

 THE MUSCLES. 



1. The Structure of Muscles. The lean meat of the 

 dead animal, as seen cut up in a butcher's stall, or when 

 cooked and brought on the table for dinner, is what we call 

 muscle. In a joint or roast of beef there are several muscles. 

 Each is surrounded by a delicate, thin membrane. This 

 membrane or tissue is loosely attached, and serves to hold 

 the muscle together and to separate 



it from neighboring ones. From its 

 inner surface this membrane sends 

 off partitions, which divide the 

 muscle into several bundles. The 

 larger bundles are divided into sec- 

 ondary ones by a finer membrane, 

 and these are again divided into 

 fibres. Looked at under the micro- 

 scope, it is discovered that even 

 these fine fibres are made up of a 

 number of very fine threads or 

 fibrils, and that each fibril is sim- 

 ply a row of cells, like a string of 

 fine beads. This gives the fibril a striped appearance. 



2. How Muscles Work. A muscle has the power of 

 contracting and relaxing. Each little fibre, under nerve in- 

 fluence, can be made to draw itself together, becoming shorter 

 and thicker, and this change taking place almost at the same 

 time amongst the thousands of fibres in a muscle, the result is 

 that, instead of lying loosely extended along the limb, the 



FIG. 16. Portions of Muscular 

 Fibre highly magnified. 



