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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



limited and inaccurate notions about the physical 

 environment, incomplete information about gross 

 anatomic. il structures, almost no evidence, and mis- 

 taken ideas about the relation of sense organs to the 

 brain or other parts of the body— they nevertheless 

 proposed theories of perception which, although 

 wrong, were reasonable. 



For example, Empedocles (ca. 490-430 B.C.I 

 mi induced a theory of sensation which can be 

 stated approximately in these words. The organ of 

 vision contains a lantern and the organ of hearing, a 

 bell or gong. The lantern in the eye is lighted and the 

 gong in the ear rung by outer light and sound, re- 

 spectively. The light in the eye and the ringing in 

 the ear are then conveyed in some fashion to the 

 'point of sense' and thus the light and sound are 

 perceived. 



Theophrastus (ca. 372-287 B.C.) criticized Empe- 

 docles' theory of hearing as follows: "Empedocles 

 explains hearing by stating that it is due to intra- 

 aural sounds. But it is strange of him to suppose that 

 he has made it self-evident how we hear by merely 

 Stating this theory of a sound, as of a gong, within 

 the ear. For suppose that we hear the outer sounds 

 by means of this gong, by what do we hear the gong 

 itself when it rings?" 3 



Translating this argument into modern terms, we 

 might think of Empedocles as representing those 

 investigators and theorists who have emphasized 

 peripheral analysis and who have proposed so- 

 called 'theories' of sensation which are actually 

 theories of end organ function. And Theophrastus 

 stated quite aptly, almost 2500 years ago, the criti- 

 1 1 m which has sometimes been made in recent 

 years, namely that having accounted for how light, 

 sound, odors or other sensory stimuli are received 

 and analvzcd In the sense organs, there still remains 

 the formidable task of discovering how this informa- 

 tion is coded and transmitted into the central nerv- 

 ous system and how it is utilized there to bring 

 about discriminatory responses 



Nbl only Empedocles and Theophrastus bul man) 

 others of the Greek philosophers contributed to the 

 <li-i listen .ind theorizing on the problems of sen- 

 sory perception. Aristotle, for example, classified 

 ihe senses into live groups: vision, hearing, touch, 

 taste .m<l smell, a classification scheme thai w.is to 

 remain a<t<-ptahlc to most scholars until .1 sixth, 



III. example <>l ih<- contrasting viewpoint! <>l Empedocli 

 and Theophrastus is taken from Beare 117). 



the muscle sense, was recognized and added at the 

 start of the nineteenth century. 



Despite this early show of interest, some 2000 

 years elapsed with little further advance in knowledge 

 of sensory mechanisms. There were, of course, im- 

 portant discoveries in the fields of physics and anat- 

 omy, discoveries which prepared the way for later 

 scientific investigations. The physics of light and 

 sound were at least partially understood and, equally 

 important for later psychological and physiological 

 investigations, instruments were developed for con- 

 trolling production of sound and light. In anatomy, 

 it became an acceptable practice (in some places 

 and in some times) to dissect animals or human 

 cadavers, and the development of the compound 

 microscope and of techniques lor preparing tissues 

 for microscopic examination led to the discoverv ol 

 many details of the structures of the end organs and 

 of their connections with the central nervous system. 



The philosophers of the seventeenth and eighteenth 

 centuries also made a contribution by emphasizing 

 the importance of the senses as the essential channels 

 by which the living organism is able to have an 

 awareness of the external environment. 



The field was set then at the beginning of the 

 nineteenth century for the launching of a scientific 

 attack upon the problems of sensory discrimination 

 or, as it might have been put by the scholars of ihat 

 period, the problem of how man knows the external 

 world. In a brief historical summary, it is impossible 

 to give due credit to all who made contributions in 

 any given field. As a mnemonic device, it is excus- 

 able, perhaps, lo select the names of some men who 

 have traditionally been accepted .is leaders in doing 

 research and in inlluencing the research and thinking 

 of their colleagues and students. 



The Modern Period 



It is fitting lo begin a discussion ot modern re- 

 search in season discrimination with .1 reference to 

 Johannes Miiller and his doctrine of specific nerve 

 energies. The doctrine or theory that Miiller ex- 

 pounded, first in 1826 and in greatei detail in 1838 



and [840, was not new with him. The same basic 



ideas can be traced back at least to John Hunter 

 in 178(1 and were expressed indirectly by Thomas 

 Young in i8oj and (putc explicitly hv Charles Bell 

 in 1H11. It was, nevertheless, Miiller who gave the 

 'theory 1 a name, even though a misleading one, and 

 who formulated in detail 10 laws or propositions and 



