— 44 — 



The Muscular System. — In a fresh specimen the mus- 

 cles appear soft and translucent ; but in specimens that have 

 been kept for a considerable time in a preservative fluid, the}' 

 are firm and opaque. The greater number of the muscles 

 are attached to the ental surface of the body-wall, where they 

 form several layers. This is well shown in the abdomen, 

 where most of the muscles are for moving the segments of 

 the body. In the head and thorax, there are numerous 

 muscles for moving the appendages of the body, and their 

 arrangement is much more complicated. 



To attempt to make a detailed stud} 7 of the muscular sys- 

 tem would require much more time than can be devoted to 

 this system in this elementary course. Only the more gen- 

 eral features of the structure of the muscles and of their 

 arrangement will be noticed. 



Note that the muscular system is composed of an immense 

 number of distinct, isolated, straight fibers, which are not en- 

 closed in tendinous sheaths as they are with vertebrates. 



Mount a few of these fibers in glycerine, and study them 

 with a high power of the microscope. Note that the fibers 

 present numerous, traverse striations, like the striped mus- 

 cles of vertebrates. 



Make a figure of a muscular fiber. 



In this outline each series or layer of closely parallel 

 fibers. is considered as a separate muscle rather than an ag- 

 gregation of muscles. It complicates the subject unduly to 

 consider each distinct fiber a distinct muscle as has been done 

 by some writers. Thus lyonet in his "Traite Anatomiqiie 

 de la Chenille, que range le bois desaiile" describes 1647 

 muscles without including the muscles contained in the vis- 

 cera or those contained in the head. 



Take a larva of Corydalis, which has been opened on the 

 ventrimeson and from which the alimentary canal and the 

 larger masses of fat have been removed, and study the en- 

 tal laver of muscles of the dorsal wall of the abdomen. 



