12 PHYSIOLOGY. 



fiber sheath. Lay a number of these side by side ; wrap 

 all in a common sheath ; let the tissue paper project be- 

 yond the threads, and here compress it into a compact 

 cylinder ; this last corresponds to the tendon. 



Connective Tissue the Skeleton of Muscle. If all 



the muscular tissue were removed from a muscle, the 

 sheaths and partitions would remain, just as they do in a 

 squeezed lemon or orange. The connective tissue forms 

 a framework for all the soft tissues of the body, and if 

 their working cells were removed, the connective tissue 

 would remain, and show more or less completely the form 

 of the part. Connective tissue, therefore, may be called 

 the skeleton of the soft tissues. Muscle consists, then, 

 essentially of a collection of soft, transparent tubes, filled 

 with the semi-fluid muscle substance. By scraping the 

 surface of a steak with a dull knife the muscle substance 

 may be obtained, leaving the connective tissue. This is a 

 good way to get the nutritious part of beef for an invalid. 



Importance of Muscles. The different materials of 

 which the body is built up are called tissues. Thus we 

 find muscular tissue, bony tissue ; nervous tissue, etc. The 

 muscles make up nearly half of the weight of the body. 

 This fact of itself should lead us to consider the muscles 

 of high importance. Add to this the facts above noted, 

 that the muscles are so largely concerned in the nutrition 

 of the body, the chief agents for its protection, essential 

 for the reception of ideas, and absolutely indispensable for 

 the expression of ideas, and we can see the reason for 

 beginning the study of physiology with the examination 

 of the muscles and their action. 



Laws of Muscle Action. The chief characteristic of 

 muscle is its ability to shorten ; incidentally, it at the 



