1932] Poliak: Ajf event Fiber Systems, Primate Cerebral Cortex 223 



Thus in the human somato-sensory system it is best developed in that 

 part conducting epicritic or gnostic tactile impulses, while in the 

 part conducting pain impulses, it remains closer to the original diffuse 

 condition (compare Foerster, 1927). Even in the most highly differen- 

 tiated system, the visual apparatus of primates, that part, correspond- 

 ing with the "peripheral" portion of the retina is considerably less 

 "spatially" organized than the macular portion. It is significant that 

 even in insects and in some of the lower vertebrates (Chameleo) the 

 visual system already shows striking perfection in the above sense 

 (Ramon y Cajal, Ramon y Cajal y Sanchez, Sanchez y Sanchez). 



With the gradual perfection of the afferent systems and their 

 peripheral receptor organs, especially those called ' ' distance receptors ' ' 

 (Sherrington), the "surrounding world" of a given species widens 

 and extends from the immediate vicinity into a larger ' ' world. ' ' As long 

 as the nervous system and its receptive and conducting mechanisms 

 are capable of receiving only those stimuli which act by contact or by 

 chemical and other changes, the ' ' world ' ' is very limited in its dimen- 

 sions and its constituents, other parts of the environment being in 

 fact non-existent. When highly perfected distance receptors, with 

 subsequent change of the nervous apparatus, are evolved, the radius 

 and the complexity of the "world" extends practically beyond any 

 limits and in this measure the appreciation and knowledge of the 

 "world" increases. 



The widening of the "world" and the ability to discriminate and 

 utilize a greater number of stimuli arising from it, is doubtless of 

 advantage to the possessor. (To illustrate this one may consider 

 countless observations of the interrelationships of various higher and 

 lower species of mammals living under natural conditions.) By giving 

 them a wider scope and an increased analytic power and in this way 

 facilitating the avoidance of noxious agents, by bringing a greater 

 amount of food into their range, and even by facilitating reproduction, 

 highly perfected distance receptors and "spatially" organized nervous 

 paths would put such a species in many respects in an advantageous 

 position in comparison to species having less developed receptors and 

 conductors. With closer study of natural conditions and of the 

 adaptation of various animal species to these it soon becomes apparent 

 that animals cannot a priori be regarded as adapted to their special 

 surroundings or their ' ' worlds ' ' and are certainly not all equally well 

 adapted. Apparent perfect adaptations are hardly more than appear- 

 ances, resulting from inadequacy of observation. Such seemingly 



