PLANT RESPONSE 125 



minor arc of this again, or on the way to it. In the present 

 series this process is peculiarly clear, in fact as typical as 

 may be. 



Of course, no mind's survey is all-comprehensive ; hence 

 a semicircle is ample for our diagram. This again we 

 may divide into parts, for the elements of an extending 

 survey, and these are four : the response of metal, of 

 plant, of animal muscle and nerve, and finally the 

 corresponding physico-psychological interpretation as far 

 as may be. A reconsideration of the facts already known 

 to physiologists of the responsive behaviour to the stimuli 

 of the physical environment of animal tissues, muscle and 

 nerve, when taken in conjunction with our physicist's 

 discoveries as regards the behaviour of inorganic matter 

 under stimulus, led him to that remarkable discovery 

 of the curve of response of metals so strictly similar 

 to the response of animal tissues already noted ; and 

 this correspondence next naturally led to that inquiry as 

 to the possibility of corresponding responses from the 

 plant, hitherto reckoned so passive and inert, which we 

 have also seen as successful. Here, then, was a new and 

 substantial unification of phenomena previously supposed 

 to be strictly confined to animal physiology, and an 

 extension of them first to the field of vegetable physiology 

 and then to that of physics, in which no such close 

 comparison had ever been suspected. Furthermore, 

 since in all sciences it is man who is observing and 

 interpreting nature, and thereby learning something 

 towards the better understanding of himself, the field of 

 human physiology is also successfully entered; especially 

 perhaps with the chapter on ' Visual Analogues,' and the 

 discovery of the binocular alternation of vision, and so on. 

 Moreover in this way it generally happens, and specifically 

 with such observations as those on ' unconscious visual 

 impression/ that the field of psychology is entered, 

 and found so far harmonious with preceding ones ; while 

 further inquiry in this field is also indicated, as will be 



