OP VERTEBRATE ANIMALS. 61 



where it is red. In the vertebrata, on the contrary, the arte- 

 ries, veins and heart contain red blood, a fluid composed of 

 colourless serum, in which corpuscules float, formed of a cen- 

 tral globule and a coloured envelope. Its composition is more 

 complicated than in the invertebrata. A whitish or slightly co- 

 loured liquid is contained in the chyliferous vessels, which 

 commence at the intestine, and in the lymphatics which arise 

 in every part of the body, both of which are very analogous 

 to veins, and terminate in them. 



The bones are hard parts, proper to the vertebrata. They 

 are situated internally and are of an organic nature, consisting 

 in a compact mass of cellular matter, containing a large pro- 

 portion of the phosphate of lime. They serve as envelopes to 

 the nervous centres; they receive and transmit the muscular 

 motions, and finally serve as support to all the parts, and 

 thereby determine the form of the body. In the invertebrata, 

 the hard parts, in general, are exuded on to the surface of the 

 skin, and consist of shells, crusts, and scales of carbonate of 

 lime, or a horny substance. This latter kind appears again in 

 the vertebrata, where it is variously disposed, as in horns, 

 scales, feathers and hairs, parts all analogous to each other, 

 both in their composition and mode of formation. We also 

 find in the vertebrata a kind of organs which is almost pecu- 

 liar to them; they are the tendons which connect the muscles 

 with the bones, and the ligaments which surround their articu- 

 lations; these liens or ties are formed of very highly condens- 

 ed cellular membrane, whose whole function consists in their 

 tenacity. 



The serous and synovial membranes are also parts formed by 

 the condensed cellular substance, disposed in the form of sacs 

 with contiguous parietes wherever the continuity of the parts 

 is interrupted; in the splanchnic cavities it separates the viscera 

 from their walls, in the moveable articulations they contain a 

 liquid which lubricates the adjoining extremities of the bones. 



55. But what distinguishes the vertebrata, is not only the 

 actions of the organs proper to them, viz: a more concentrat- 

 ed nervous system, whose central parts are more voluminous, 

 whence results an appearance of intelligence which distin- 



