22 THE REASON WHY 



1 How poor, how rich, how abjest, how august, 

 How complicate, how wonderful is man." YOUNG. 



elasticity. Without such elasticity, a jar would reach the more 

 delicate organs, even in the very recesses of the body, at every 

 violent motion ; and every joint would crack by the attrition of the 

 surfaces of the bones. 



58. What is a muscle? 



A muscle is composed of long slender fibres, which possess the 

 power of contracting, and are everywhere enveloped in common 

 cellular membranes ; the fibres become fewer as they approach the 

 extremity of the muscle, and ultimately terminate. The cellular 

 substance that envelopes them being thus freed from the muscular 

 fibres, joins more closely together, and forms itself into a white, 

 round, or flattened tendon. When the muscular fibres contract, their 

 power is united on the tendon, and drawing it up, makes it perform 

 the action of a pulley. 



59. Different muscles accomplish very different purposes. Some of them 

 draw down the limb or part to which they are attached, if it has a moveable joint, 

 and is placed under the part of the body in which it acts. Others elevate and ex- 

 tend the moveable parts to which they belong, and are placed on the superior 

 surface. Some muscles, also, move on the parts obliquely, as the oblique muscles 

 of the eye, and others make them describe a semi-circle, as in the motions of the 

 neck, arms, legs, &c. ; some elevate the upper eyelids ; others contract them, as the 

 eyebrows ; or wrinkle them, as the extremities of the lips. The muscles also act on 

 the legs, arms, fingers, toes, &c., in moving them to either side. Another example 

 of their power is instanced in the forearm, legs, &c. The beauty of the mechanism 

 of the muscles is also evinced in the abdomen, where some are transverse, others 

 straight, oblique, &c. 



60. What are the nerves ? 



They are a species of fine thread running from every part of the 

 body, charged with exquisite sensibility, by which they convey 

 the impression or commands between our will and our muscles. 



The vital power of a muscle resides in the nerves, and is nervous. Its irritablt 

 power is the property by which it feels and acts, when stimulated without conscious- 

 nets. It is an inherent principle belonging to its constitution, and remains some time 

 after death. Ligaments and tendons support the same weight, whether dead or alive ; 

 fcut a living muscle that lifts one hundred pounds with ease, cannot, after death, 

 raise twenty pounds without danger of rupture. When a muscle is newly cut from a 

 limb, it palpitates and trembles for a considerable time it cannot be nervous power 

 'hat thus makes it irritable ; for the nerves being separated from their organ, aif 



