94 ANATOMY FOR NURSES [Chap. VII 



stances of which it is composed are split and oxidized into simpler 

 substances, i.e. water, carbon dioxide, and sarcolactic acid. At 

 the same time heat is generated, energy is set free, and various 

 waste products are formed. Heat is a familiar result of muscular 

 exercise. The liberation of energy enables the muscle to do its 

 required work. The waste compounds must be eliminated, and, 

 except in cases of prolonged contractions, the system is able to get 

 rid of thep readily. Prolonged contractions result in fatigue, and 

 this means two things : (1) an accumulation of waste substances, 

 known as fatigue poisons, (2) a loss of nutrient material. A 

 period of rest furnishes opportunity for these poisons to be carried 

 to the excretory organs by the blood, and fresh nutritive materials 

 from the digestive organs carried by the blood to the muscle. In 

 cases of extreme fatigue that are the result of prolonged overwork 

 of a muscle or muscles, the fatigue poisons have the same effect 

 that the toxins of tetanus have, and the over-contracted condition 

 is spoken of as tetanus of the muscle. Writer's cramp with its ac- 

 companying stiffness and pain is an example of this condition. 

 In such cases massage improves the circulation of the blood and 

 IjTiiph, thus helping the elimination of fatigue poisons, and brings 

 about a condition of relaxation. 



Skeletal Muscles. — The muscles are separate organs, each 

 muscle having its own sheath of connective tissue, called epimy- 

 sium. They vary in size from a fraction of an inch to nearly twenty- 

 four inches (600 mm.) and are very diverse in form. In the trunk 

 the muscles are broad, flattened, and expanded, forming the walls 

 of the cavities which they enclose. In the limbs they are of con- 

 siderable length, forming more or less elongated straps. A 

 typical muscle is described as consisting of a body and two ex- 

 tremities. The body is the red contracting part, and the extremi- 

 ties arc the ends where they are attached. 



Attachment of the muscles to the skeleton. — Muscles are at- 

 tached 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 inserting their fibres into the bones. 

 Where one muscle connects with another, each muscle ends in 

 expanded form in a flat, fibrous membrane called aponeurosis. 



