68 ANATOMY FOR NURSES. [Chap. VI. 



ing sheaths for the smaller bundles, connecting and binding the 

 fibres and bundles together, and conducting and supporting the 

 blood-vessels and nerves distributed to the muscle fibres. 



The muscles vary greatly in shape and size. In the limbs 

 they are of considerable length, forming more or less elongated 

 straps ; in the trunk they are broad, flattened, and expanded, 

 forming the walls of the cavities which they enclose. 



They are attached to the bones, cartilages, ligaments, and 

 skin in various ways, the most common mode of attachment 

 being by means of tendons. The muscular fibres converge as 

 they approach their tendinous extremities, and gradually blend 

 with the fibres of the tendons, the tendons in their turn insert- 

 ing their fibres into the bones. Sometimes the muscles end in 

 expanded form in the flat fibrous membranes, called aponeuroses. 

 Again, in some cases, the muscles are connected with the bones, 

 cartilages, and skin, without the intervention of tendons or 

 aponeuroses. 



In the description of muscles it is customary to speak of the 

 attachments of their opposite ends under the names of origin 

 and insertion, the first term origin being usually applied to the 

 more fixed attachment ; the second term insertion being applied 

 to the more movable attachment. The origin is, however, 

 absolutely fixed in only a very small number of muscles, such 

 as those of the face, which are attached by one end to the bone, 

 and by the other to the movable skin. In the greater number, 

 the muscle can be made to act from either end. 



The muscular tissue or flesh forms a large proportion of the 

 weight of the whole body. The following has been calculated 

 for a man of one hundred and fifty pounds' weight from the 

 tables of Liebig: skeleton, twenty-eight pounds; muscles, sixty- 

 two pounds ; viscera (with skin, fat, blood, etc.), sixty pounds. 



The total number of voluntary muscles may be stated at 

 three hundred and eleven. It is not necessary for us to be able 

 to distinguish more than a few of the most prominent. We 

 may conveniently classify these into two groups : — 



1. Chief muscles of the head and trunk. 



2. Chief muscles of the limbs. 



Chief muscles of head, face, neck, and trunk. — The chief muscles 

 of the head are the occipital and frontal muscles, which, united 



