ANIMAL ORGANIZATION . 115 



progressive motion, and sometimes fashioned 

 into weapons of offence. In this class should be 

 included all the varieties of hair, such as wool, 

 fur, feathers, bristles, quills, and spines, as well 

 as the more ordinary kinds of hair. All these 

 resemble the cuticle in their chemical compo- 

 sition, differing only in their degrees of hardness 

 and condensation. Horn is formed of the same 

 material as hair ; as are also the nails, the hoofs, 

 and the claws of quadrupeds, and the scales of 

 fishes, reptiles, and other animals. The integu- 

 ments of insects, and especially their more solid 

 and horny coverings, contain, however, as will 

 hereafter be noticed, a peculiar chemical prin- 

 ciple termed Entomoline. 



All these parts seem to be but remotely con- 

 nected with the vital actions of the system with 

 which they are associated; and it is doubtful 

 how far they are to be considered as apper- 

 taining to the living portion of the body, or as 

 mere extraneous appendages. Yet, however they 

 may differ in their forms, uses, and external ap- 

 pearance, they all are produced by the same 

 kind of vascular structure, variously arranged to 

 suit the particular circumstances in each case : 

 and the mode of their developement and growth 

 is essentially the same in all. 



An extremely delicate and finely organized 

 pulp, composed partly of a congeries of minute 

 vessels, and partly of a gelatinous substance, in 

 which these vessels are embedded, constitutes 



