NATURE OF THE MUSCLES. 91 



enlarged so as to present a greater surface than the 

 body of the bone, and form what are called processes, 

 for the obvious purpose of affording greater room ; 

 and, secondly, instead of all the fleshy fibres of a 

 muscle being prolonged to its points of attachment 

 at the bone, they, with few exceptions, terminate 

 gradually, as they proceed from the belly, in a white 

 shining tendon, of a much smaller size than the 

 muscle, but of great strength, which is inserted into 

 the bone. These tendons, or sinews as they are 

 occasionally named, conduce greatly to symmetry, 

 elegance, and freedom of motion ; and may be traced 

 under the skin on the back of the hand, and in the 

 very powerful specimen at the heel, called the ten- 

 don of Achilles. The hamstrings are another ob- 

 vious example, and may be easily felt becoming 

 tight when an effort is made to bend the knee. 

 There are a few muscles not attached to bones by 

 either extremity, and also a few which have no ten- 

 dons. Those which surround the eyebrows, the 

 mouth, the gullet, and some of the other natural 

 passages are of the former description ; as is also 

 the heart. Some of the muscles of the trunk have 

 no tendons, but these are few in number, and may 

 at present be considered exceptions to the general 

 rule. 



In man, and in most of the animals with which 

 we are familiar, the muscles are of a red colour. 

 This, however, depends entirely on the blood which 

 they contain ; for so far is the colour from being 

 essential to their constitution, that it may be de- 

 stroyed by washing out the blood which produces 

 it, the muscular substance remaining in other re- 

 spects unchanged. Hence the colour of the muscles 

 varies with that of the blood, is dark where it is 

 dark, pale where it is pale, and white where it is 

 white. The true characteristic of muscular fibre 

 is contractility, or the power of shortening its substance 



