SUMMARY. 249 



arteries, for exciting them, and connecting them more particularly with the functions of 

 the organ on which they are about to terminate. 



After the birth of an animal, something deleterious to the nervous system is 

 generated with the nourishment, and requires to be eliminated, for preserving the vital 

 properties of the body. This is effected principally by respiration ; it is also assisted 

 by the liver and kidneys, and the absorbent system ; and these organs are evolved in a 

 greater or less degree, according to the extent and quality of the nervous system. 

 Although the nervous system cannot continue its functions without the lungs or some 

 compensating organs, these are not made for the nervous system only, as every part of 

 the body requires a share of blood purified in the same manner, that there may be an 

 harmonious action throughout. 



Independently of the blood, there is a more enduring vitality of the solids in some 

 animals than in others. Amphibia with a very slow circulation of blood, moderately 

 influenced by oxygen, under peculiar circumstances can retain it much longer than 

 birds and mammalia. The shorter the period elapsed since the foetal state, the less 

 liable is the body to death from a want of the changes in the blood by oxygen, in some 

 measure because the nervous system is not so fully developed, and has lately been so 

 accustomed to venous blood, but principally because some remains of the vicarious 

 passages continue, and keep up a circulation, which the passive lungs would otherwise 

 have prevented. 



In considering the functions of the nervous system, it is necessary to look further 

 than the organs of the circulation, the influence of the blood itself, and the several 

 processes by which the nourishment necessary for preserving vitality is to be prepared 

 and purified. The material nervous system must have a source of animation for its 

 own purposes, for enabling it to perform its higher functions, and this is the nervous 

 element which must, however, be continued in efficiency by oxygenised blood. Through 

 this nervous element the nervous system becomes capable of acting with the next 

 higher spiritual element in animals, for producing the instinct, the will, the sensitive, 

 and involuntary powers. However difficult the comprehension of the nature or even of 

 the presence of spiritual agents may be, their existence, efficiency, and power, must 



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