LIFE: ITS NATURE, ORIGIN AND MAINTENANCE 27 



feature of the evolution of the Metazoa. By and through it all impressions 

 reaching the organism from the outside are translated into contraction or 

 some other form of cell-activity. Its formation has been the means of 

 causing the complete divergence of the world of animals from the world of 

 plants, none of which possess any trace of a nervous system. Plants react, 

 it is true, to external impressions, and these impressions produce profound 

 changes and even comparatively rapid and energetic movements in parts 

 distant from the point of application of the stimulus as in the well-known 

 instance of the sensitive plant. But the impressions are in all cases propa- 

 gated directly from cell to cell not through the agency of nerve-fibres; and in 

 the absence of anything corresponding to a nervous system it is not possible 

 to suppose that any plant can ever acquire the least glimmer of intelligence. 

 In animals, on the other hand, from a slight original modification of cer- 

 tain cells has directly proceeded in the course of evolution the elaborate 

 structure of the nervous system with ail its varied and complex functions, 

 which reach their culmination in the workings of the human intellect. 

 ' What a piece of work is a man ! How noble in reason ! How infinite in 

 faculty ! In form and moving how express and admirable ! In action 

 how like an angel ! In apprehension how like a god ! ' But lest he be 

 elated with his psychical achievements, let him remember that they are but 

 the result of the acquisition by a few cells in a remote ancestor of a slightly 

 greater tendency to react to an external stimulus, so that these cells were 

 brought into closer touch with the outer world ; while on the other hand, 

 by extending beyond the circumscribed area to which their neighbours 

 remained restricted, they gradually acquired a dominating influence over 

 the rest. These dominating cells became nerve-cells ; and now not 

 only furnish the means for transmission of impressions from one part of 

 the organism to another, but in the progress of time have become the 

 seat of perception and conscious sensation, of the formation and 

 association of ideas, of memory, of volition, and all the manifestations of 

 the mind. 



The most conspicuous part played by the nervous system in the pheno- 

 mena of life is that which produces and regulates the general movements 



of the body movements brought about by the so-called 

 voluntary muscles. These movements are actually the 

 system. Voluntary result of impressions imparted to sensory or afferent 

 movements. nerves at the periphery e.g., in the skin or in the 



several organs of special sense ; the effect of these impressions may not be 

 immediate, but can be stored for an indefinite time in certain cells of the 

 nervous system. The regulation of movements whether they occur 

 instantly after reception of the peripheral impression or result after a cer- 

 tain lapse of time ; whether they are accompanied by conscious sensation 

 or are of a purely reflex and unconscious character is an intricate process, 

 and the conditions of their co-ordination are of a complex nature involving 

 not merely the causation and contraction of certain muscles, but also the 



