the brain with the iiuiss ot the body, within one species, as well as 



from species to s|)ecies. 



Still it remains, however, an open ipiestion why tlie lengths of the 



images, as measured by tiie iinmber of sense-eiemetits, increase 

 1 



exactly as L^ = TJ^-^^-. 



In order to find an answer to it, we must consider, that the eye 

 distinguishes itself fiom the other senses by giving at a distance a 

 representation of the exact place of the (^nergy-source that acts as a 

 stimulus. Consequently it orientates about the direction from which 

 that stimulus comes. Object and image, that is the place of the 

 stimulated sense-elements, answer to each other. 



Under these circumstances the distance to the objects must 

 exactly stand in the mentioned relation to the linear dimension of the 

 body. Indeed the receptive nerve-elements of the retina placed in the 

 linear dimension of the image, increase then numerically in the propor- 

 tion of L*^^^- in the larger animal, their mass in the linear dimension 

 as L, their mass for the surface of the image as />^ But that mass 

 determines the amount of the transition of energy that is connected 

 with the stimulation of the sense-elements. 



It appears now that the long since known intimate coimection of 

 the organ of vision, as exquisite sense of room finding its principal 

 function in governing the movements, can be expressed in a definite 

 measure^). As in the movements of animals, differing in the size of 

 their bodies, the mass that is to be removed, increases in the pro- 

 portion of /v^ the muscle-power however only as U, an L-foId 

 sensu-motorical stimulation is required for it. And as all senses are 

 more or less, as the optical sense is absolutely, organs of room, 



their receptive elements must; in the aggregate, increase in mass in 



1 



that proportion of L, that is in linear dimension as X^ in super- 



i 2 



ficial dimension as L^ , or S^ . But the nerve-fibres, the peripherical 

 extremities of which are connected with sense-elements in the retina 

 and also in all other sensitive surfaces, and the corresponding cell 



o 



9 JL 



masses in the brain must increase as V S- = S"^ = S^-^--. 



The denominator of the coefficient — - can thus be explained as 



a relative reduction of the brain of the larger animal i)roportional 



1) In a slfiking way this cüiineclion is demonstrated by Putter (1. c. p.p. 85 et 

 seq, and p.p. 402 el seq ). 



