CHAPTER 



SECOND. 



THE MOVING POWERS OF THE SYSTEM. — MYOLOGY, OR THE 

 HISTORY OF THE MUSCLES. 



DEFINITIONS AND DESCRIPTIONS. 



228. Microscopic Structure of Muscle. — The Muscles, 

 known as flesh or lean meat, compose a large part of the 

 extremities, and the covering of the trunk. To the naked 

 eye they appear to be fibrous, and, with the assistance" of the 

 microscope, these fibers are found to be bundles — called Fasci- 

 culi — of still smaller fibers, called Ultimate Fibers. These 

 seem to be polygonal in form, and with an average diameter 

 of j^oth of an inch in man, though in some of the lower ani- 

 mals their size is much less. 



View of the stages of development of FlG. 120. 



Muscular Fiber. 1, A Muscular Fiber of 3 I i I I 



Animal life enclosed in its Sheath or ,js2^g* "AS ill I I 



229. Fibrils. — The ulti- ' 

 mate fibers are still further divisible *into what are termed 

 Fibrils. These have an average diameter of about T¥ £o o th 



Myolemma. 2, An Ultimate Fibril of the 

 same. 3, A more highly magnified View 

 of Fig. 1, showing the true nature of the 

 Longitudinal Striae, as well as the mode of 

 formation of the Transverse Striae. The 

 Myolemma is here so thin as to permit the 

 Ultimate Fibrils to be seen through it. 4i 

 A Muscular Fibre of Organic life with two 

 of its Nuclei ; taken from the Urinary Blad- 

 der, and magnified 600 Diameters. 5, A 

 Muscular Fibre of Organic life from the 

 Stomach, magnified the same. 



228. What is lean meat ? How does muscle appear to the naked eye? What are the 

 three microscopic elements ? Describe each. 229. What is the diameter of the Fibrils? 



