APPARATUS OF MOTION. 



77 



158. A variety of appendages are attached to these 

 rings, such as jointed legs, or in place of them stiff bristles 

 oars fringed with silken threads, wings either firm or mem 

 branous, antennae, movable pieces which perform the office 

 of jaws, &c. But however diversified this solid apparatus 

 may be, it is universally the case that the rings, to which 

 every segment of the body may be referred as to a type, com-, 

 bine to form but a single internal cavity, in which all the or- 

 gans are enclosed, the nervous system, as well as the organs 

 of vegetative life, (63.) 



159. The muscles which move 

 all these parts have this peculiar- 

 ity, that they are all enclosed with- 

 in the more solid framework, and 

 not external to it, as in the verte- 

 brates ; and also that the muscular 

 bundles, which are very consider- 

 able in number, have the form of 

 ribbons, or fleshy strips, with par- 

 allel fibres of remarkable white- 

 ness. Figure 27 represents the 



Fig. 27. 



disposition of the muscles of the caterpillar which destroys 

 the willow, (Cossus ligniperda.) The right side represents 

 the superficial layer of muscles, and the left side the deep- 

 seated layer. 



160. The Vertebrata, like the articulated animals, have 

 solid parts at the surface, as the hairs and horns of mam- 

 mais, the coat of mail of the armadillo, the feathers and claws 

 of birds, the bucklers and scales of reptiles and fishes, &c. 

 Hut they have besides this, along the interior of the whole 

 body, a solid framework not found in the invertebrates, well 

 known as the SKELETON. 



161. T.he skeleton is composed of a series of separate 

 bpnes called vertebras, united to each other by ligaments. 



7* 



