PHYSICAL BASIS OF SENSATION 



659 



appeared moderate. Records were then made under increas- 

 ing stimulus i, 2, 3, 4, 5. ... It will be seen from these 

 (fig. 402) that increasing stimulus induces at first a rapid 

 augmentation of the negative response, after which a limit 

 is reached. 



The same characteristics I find to hold good of the 

 response of plant-nerve (fig. 403). Here the response-records 

 were commenced at a point just above that of transition. 

 Now, if these particular relations between stimulus and 



response be due, in the case 

 of man, to some specific 

 psychic reaction, then the 

 same must also be true not 



FIG. 402. Response of Optic Nerve 

 of Ophiocephalus to Arithmetically 

 increasing Stimuli i, 2, 3, 4, 5, 6, 7 



FIG. 403. Mechanical Response 

 of Nerve of Fern to Arithmetic- 

 ally increasing Stimulus 



only of the animal but also of the plant. And further, the 

 records themselves, being mechanical, were direct records 

 of undeniably physical changes. Even in the case of the 

 inorganic, again, the same characteristic relations obtain, as 

 we shall find in the next figure. Hence it is not true that 

 the relation between stimulus and the responsive reaction is 

 different in the inorganic from what it is in those living 

 nervous tissues whose changes we perceive as sensation- 

 That is to say, it is determined, in all cases alike, by the 

 same underlying physical factors, 



U U 2 



