FUNCTIONS OF QUADRUPEDS. 7 



few of the quadrupeds it is long and prehensile, or capable 

 of being coiled round objects, to supply the place of a hand 

 in fastening or suspending themselves. The tails of most 

 quadrupeds are covered with hair : those of some of the 

 Glires are naked, or covered with scales, and thinly scattered 

 with hair. The tails of the Armadillos are composed of 

 horny rings. 



The flesh of quadrupeds is composed of vessels, fibres, 

 and nerves, and has the denomination of muscles. Each 

 muscle is made up of many fibres, united together into little 

 bundles, and appears red and soft, from the blood with 

 which it is constantly drenched. The fibres at the extre- 

 mities of the muscles are called tendons: they are closer and 

 more firm than the others, and are of a silvery white colour. 

 It is by means of these that the muscles are attached to the 

 bones. Their substance is almost entirely gelatinous; and, 

 in a healthy state, they possess neither sensibility nor irrita- 

 bility. 



The muscles are the organs of motion ; and when the 

 body is in a state of health, the will exercises a constant and 

 prompt power over them, A small number, however, are 

 not subject to the influence of the will. These produce in- 

 ternally the movements which are necessary to life, and 

 which cannot be interrupted ; such as the motion of the 

 heart and the intestines. The motion of some other muscles, 

 as those connected with respiration, appears to be of a 

 mixed nature ; we can stop their action, but their motion 

 is continued by habit, without our formally willing, or with- 

 out our being even conscious of it. 



Each muscle is inclosed in a thin covering called cellular 

 membrane. This descends into the substance of the muscle, 

 connecting and surrounding the most minute fibres, and af- 

 fording a support to the vessels and nerves. The muscles 



B4 are 



