OR OSSEOUS SYSTEM. 35 



substances, termed chitine and coccine, and consolidated 

 by small proportions of the phosphates of lime, magnesia, 

 and iron. As in other entomoid classes, the trunk is 

 surrounded with hollow rings or segments, which on the 

 anterior parts of the body support lateral appendices ap- 

 propriated to sensation, mastication, or progressive mo- 

 tion ; and consequently, on these anterior portions of the 

 body, the segments are more consolidated and more firmly 

 united together than in the flexible and capacious pos- 

 terior part. There are generally thirteen segments dis- 

 tinguishable in the trunk of insects, of which the anterior 

 forms the head, the next three the thorax, and the posterior 

 nine the abdomen. The annexed diagram from Carus shows the 

 form and position of these parts of the skeleton viewed from be- 

 hind in the calosoma sycophanta, (Fig. 16.) a coleopterous in- 

 sect. The body of insects generally tapers more or less at both 

 ends, and the terminal segments before and behind are 

 those least developed ; those composing the head indeed 



FIG. 16. 



