84 GENERAL CHARACTERS OF VERTEBRATED ANIMALS. 



where this is the case, most of these parts are but repetitions of 

 one another. It is by the variety existing in the form and struc- 

 ture of their several organs, and in the perfection with which each 

 is adapted to perform its allotted function, that the Vertebrata 

 are chiefly characterised. It is manifest that the structure of 

 such animals must be regarded as more elaborate, than that of be- 

 ings, in which the number of dissimilar parts is small, and every 

 one of them capable of discharging a variety of offices ; and that 

 their functions must be performed with more energy and complete- 

 ness^ when carried into effect by instruments peculiarly adapted 

 to each, than when several are the result of the actions of one 

 organ. Hence we are justified in ranking the Vertebrata as the 

 highest group in the Animal scale, independently of its being the 

 one which contains Man. But we are not justified in speaking 

 of the animals composing it, as more perfectly constructed than 

 any others ; since, in the eye of the Creator, they must be all 

 equally perfect. In every one, the adaptation between the ac- 

 tions of its several parts must be complete; or it could not main- 

 tain its existence. And it should not be less wonderful to us, to 

 meet in the Zoophyte with a simple structure, capable of per- 

 forming all the functions of absorption, assimilation, respiration, 

 and secretion ; than to contemplate the numerous and elaborately- 

 constructed organs, by which these several operations are respec- 

 tively performed in the Vertebrated animal. 



62. The development of all the organs in the Vertebrata 

 seems to be subservient to that of the Nervous System ; their 

 object being to give to it the means of the exercise of its powers. 

 In almost every animal of the group, we find that the brain and 

 spinal cord bear a much larger proportion to the entire bulk of the 

 body, than do the nervous centres of any Invertebrated animal; 

 and in Man, this proportion is greatly increased. It is not only 

 in the actual bulk of the organs, that we see the importance here 

 given to the nervous system ; for this is still more shown by the 

 quantity of blood which is transmitted to them. Thus it is cal- 

 culated that the brain of Man receives about a fifth or sixth part 

 of the whole blood in circulation ; although its weight is not more 

 than a fortieth or fiftieth part of that of the entire body : and 



