OP THE MUSCLES. 219 



Each muscle is distinguished into three parts, called 

 the origin, venter or swell, and the insertion or termin- 

 ation. 



The origin is that part by which the muscle is attach- 

 ed at its upper end ; the swell is the thickest or most 

 conspicuous part, and that which makes up the chief 

 bulk of the whole ; the insertion is the smaller, or tendi- 

 nous part, being that by which it is attached at the end 

 opposite to the insertion. 



These three parts are shown by Fig. 121, of which a 

 Fig. 121. is the origin, b the swell, 



and c the tendinous in- 

 sertion. - The tendons, 

 in which most of the 

 muscles end, are strong, 

 white glistening cords, 

 known in the feet of an- 

 i imals under the name of 

 sinews. The tendon in which the muscles of the leg 

 terminate, and which is fastened to the bone of the heel, 

 is a good example of this part of the human frame. It 

 is called the Tendo Achilles, and is said to have been so 

 named, because as fable reports, Thetis, the mother of 

 Achilles, held him by this part when she dipped him into 

 the river Styx, to make him invulnerable. Hence that 

 famous hero was said to be proof against all weapons, ex- 

 cept in the right heel. 



Names of the Muscles. Every part of the human 

 body which we ca\[ fleshy, is covered with muscles, some 

 parts having several layers, one over the other. They 

 all have distinct names by which they are discriminated 

 by anatomical writers. Most of these names are deri- 

 ved from those of the parts where they are situated. 

 Thus the muscles of the breast are called the pectoral 

 muscles, from pectus, the breast ; and those extending 

 from the shoulder to the elbow, are called the brachial 

 muscles, from brachium, the arm. Some are however 

 named from their shapes, as long, broad, or triangular. 



What are the three parts into which a muscle is distinguished 1 What 

 are tendons 7 What are the names of the muscles generally derived from 1 



