PLANTS CONSTRICTED ON A SURFACE TYPE. 



a point in comparison with the world from which it gathers its intelligence, is the whole 

 mass of the brain ! Is it not affected by light which has come from systems of suns at 

 the uttermost ends of the universe ! Does it not watch the rotation of double stars of 

 different colours, which occupy enormous periods of time to complete their revolutions, 

 and are situated at almost immeasurable distances ! 



391 Nervous action in animals is thus carried on by a complicated mechanism, and 

 the nervous agent, though ordinarily spoken of as "one and indivisible," presents itself 

 to our view as the reunion of many forces, or as one force with many modifications. 

 To the immaterial and responsible principle which is within us, it stands in the char- 

 acter of a minister and messenger, to connect it with the outward natural world, to 

 gather impressions and enable it to react on material things. Hence arises that sub- 

 division of functions of which we have been speaking, a subdivision not only affecting 

 external impressions, but also the corresponding individual actions. The nervous and 

 optical mechanism of the eye is so arranged as to have entire charge over the recep- 

 tion of impressions conveyed by the luminiferous ether ; the auditory mechanism of the 

 ear is constituted so as to receive undulations of gaseous bodies like atmospheric air; 

 and, correspondingly, if intelligence has to be communicated to a distance, and received 

 bv other minds through the agency of a visual organ, the motor nerves of the hand are 

 put in action, the fingers move, and letters appear upon the paper. 



392. In steam-engines or other automatic machines, our admiration is chiefly aroused 

 bv the regular and consentaneous manner in which their movements are performed. 

 At the proper instant the proper valves are sprung, and the intricate motions go on 

 with regularitv. No one can have seen a large cotton or silk factory in which the 

 machinerv is driven by one of these engines without being struck with this remark. 

 Perhaps it is weaving an elaborate pattern, and, with a discretion that almost simulates 

 intelligence, is putting in or leaving out the variously- colo'ured threads. To produce 

 this, a series of contrivances is made to intervene between the point of action and the 

 motive force, and accordingly as the result is different, so must that intervening mech- 

 anism vary. In animal systems, the same observation holds good : impressions which 

 come to us from the external world, and movements which result from mental opera- 

 tions, are all transmitted by their proper channels. 



393. From the time of Aristotle, it has been observed that the type on which vege- 

 tables have been constructed bears a remarkable relation to the type of animals. In 

 the latter all the processes of organic life, such as digestion, respiration, secretion, are 

 carried forward in interior cavities ; in the former they are surface actions. Thus, the 

 stomach, the digestive organ, is enclosed in an interior space, but the leaf, which is the 

 analogous organ for plants, is freely exposed, and digestion takes place upon the sur- 

 face. So, too, with respiration, the lungs of the mammalia are placed within the walls 

 of the chest, and receiving oxygen from the air, transmit it by the arterial blood to the 

 capillary vessels, in which the combustion of carbon is going on; but when in plants 

 the same result is to be attained, oxydation takes place on the petals of the corolla, 

 which is another surface action. In animals the attempt is to centralize everything, 

 to make all the functions subservient to the perfect development of one focal point, to 



