36'2 THE MECHANICAL FUNCTIONS. 



of bone which constitute tlie primary forms of the 

 vertebrae, and which contain the spinal cord; but 

 the rings of insects include the viscera, whereas the 

 spinal cord alone is contained within the vertebral 

 circles. Vertebrated and articulated animals agree, 

 also, in having the head placed at one extremity, 

 distinct from the trunk, and containing the princi- 

 pal organs of the senses. 



An approximation is apparently made towards 

 an internal skeleton in thecephalopodous Mollusca ; 

 where we find a central body, cartilaginous in 

 some species, calcareous in others. In the Loligo, 

 it has a long and slender shape, and is pointed at 

 the end, like the blade of a sword ; it bears, as we 

 shall hereafter notice, some resemblance to the car- 

 tilaginous spine of the fish called the Mijxine, or 

 Gastrobrcmclms, which does not enclose the spinal 

 marrow, but only admits it to pass along a groove 

 in its upper edge. But the search after remote 

 analogies of this kind has been carried much beyond 

 the boundaries of rational inquiry ; and by enlisting 

 the imagination in the pursuit, has too often led 

 naturalists far away from the path of truth, and the 

 reality of nature. All that can with safety be said 

 is that there exist many perceptible links of con- 

 nexion among all the classes of created beings^ 

 even in those apparently the most remote from one 

 another ; so as to render it clear to the philosophic 

 naturalist, that all the races of animated beings are 

 members of one family, and the offspring of the 

 same provident parent, who has matured all his 

 plans on a deeply premeditated system, and who 

 dispenses all his gifts with the most salutary regard 

 to the general welfare of his creatures. 



M 



