624 



SCIENCE 



[N. S. Vol. XLV. No. 1173 



tary chemical and physical aspects of the 

 environment. Touch, moreover, gives us 

 form and position and passes imperceptibly 

 into that vague but enormously important 

 sense, the muscle sense, through which the 

 movements of our bodies, our limbs and 

 other parts are checked and adjusted and 

 the whole problem of spatial relations re- 

 ceives a new setting. Closely allied to these 

 senses is the ear as an organ of equilibra- 

 tion responding to the pull of gravity and 

 to our sudden changes in position and, like 

 the muscle sense, affecting our conscious 

 states so slightly that we scarcely know we 

 have such a sense till on sea or on train ex- 

 cessive stimulation due to the unusual form 

 of motion draws on characteristic discom- 

 forts. Next may be mentioned the ear as 

 an organ of hearing attuned to the sounds 

 of nature and in man attentive to the voice, 

 that marvelous means of signaling whereby 

 the momentary mental life of one human 

 being can be quickly and accurately im- 

 posed upon another. And finally the eye 

 with its responsiveness to light three thou- 

 sand times greater than that of the most 

 sensitive photographic plate, adjusted to 

 color and to form, and in no whit behind 

 the ear in its social significance. Thus our 

 sense organs literally deluge us with a flood 

 of messages concerning our surroundings 

 and yield us all the elements out of which 

 our mental life is built. In fact there is 

 good reason to believe that without this sen- 

 sory inrush consciousness itself could never 

 come into being. The newborn brain is not 

 unlike the western desert ; only after irriga- 

 tion in the form of sensory inflow does con- 

 sciousness begin to blossom. 



Considering the enormous significance of 

 the sense organs for man as the means of 

 supplying him with the content of his mind, 

 it is not surprising that in attacking the 

 problem of the brain and our mental states 

 students should have made their approach 



almost entirely from the sensory side. The 

 quality and quantity of sensations were ex- 

 haustively investigated and even the cen- 

 tral nervous organs were dealt with from 

 the standpoint of their sensory relations. 

 In brief, the sensation became more and 

 more the established unit in considering 

 nervous action, and we were led to inter- 

 pret the nervous states of the whole range 

 of lower animals by the sense organs they 

 were shown to possess. If a particular 

 worm or jelly fish had an unusually de- 

 veloped eye, it was assumed that the given 

 animal enjoyed an excess of sensation akin 

 to sight with us as compared with its less 

 fortunate neighbors. If a crawfish inhabit- 

 ing caves possessed degenerate eyes, but was 

 covered with enormously developed tac- 

 tile hairs, it was supposed to have realized 

 something of that excessive development of 

 touch which we know is characteristic of 

 the human blind. Thus the well-known re- 

 lations of our sense organs to our mental 

 life gave a basis for the assumption of cor- 

 responding mental states in the lower ani- 

 mals. 



If, however, the sources of our nervous 

 organs are such as I have sketched, it is ex- 

 tremely doubtful whether the interpreta- 

 tions just mentioned are at all justifiable. 

 In the beginning sense organs had nothing 

 whatever to do with the delivery of mes- 

 sages to a conscious center. They were or- 

 gans concerned merely with the calling 

 forth of muscular movements. The animal 

 with especially developed eyes or with un- 

 usual organs of touch is not necessarily en- 

 dowed with special sensations in these di- 

 rections; it may be an animal merely 

 adapted to respond with unusual delicacy 

 to light or touch and without central ner- 

 vous relations at all. Thus the sense organs 

 in the lower animals come to have a very 

 different significance from that formerly at- 

 tributed to them. They are special means 



