March 6, 1908] 



SCIENCE 



383 



regards neurone transmission when an act 

 previously carried on with painstaking, 

 conscious effort, becomes so habitual and 

 automatic that conscious control can be, 

 and often is practically, done away with. 

 Does this involve the use of pathways below 

 the level of the cerebral cortex, or does it 

 simply mean decreased resistance in cor- 

 tical neurone systems, consciousness being 

 the expression of such resistance? Our 

 basal conception of the relation of con- 

 sciousness to the nervous system will be 

 determined in no small measure by a con- 

 elusive answer to this question. Despite 

 much dogmatic assertion and certain very 

 interesting recent experimental investiga- 

 tions, the problem is still unsolved. 



We wish also and particularly to know 

 what portions of the nervous system, or 

 what modes of nervous action are primarily 

 responsible for the great subdivisions of 

 our mental life. In a rough way we have 

 already learned something in reply to such 

 questions regarding the portions of our 

 brain responsible for certain of our sensa- 

 tions and movements and even for certain 

 of our ideational activities. But the de- 

 tails are still very hazy. We should be 

 glad for a more definite knowledge of the 

 differences in cortical action which dis- 

 tinguish sensations and perceptions from 

 ideas and images. Here again dogmatism 

 runs far in advance of well-organized and 

 demonstrable fact. We should also wel- 

 come most enthusiastically any funda- 

 mental illumination as to the physiological 

 basis of memory. 



We want to know much more than the 

 specialist can now tell us about the struc- 

 ture and function of sense organs. Be- 

 havior is simply a generic term for mus- 

 cular movements made originally in re- 

 sponse to sensory stimulations of one kind 

 or another. It is obvious that we must 

 know the characteristics of these sensory 

 excitations before we can adequately 



iinderstand the reactions which are made 

 to them. This is peculiarly true of com- 

 parative psychology, with its interest in the 

 mental processes of animals, but it is 

 equally true at bottom in the case of human 

 psychology. We want, for example, to 

 know the structure of the retina in the 

 lower animals and especially those whose 

 vision is not binocularly unitary, and we 

 also want to know the facts about the 

 visual conduction pathways in the central 

 nervous system in the case of such animals. 

 This knowledge we desire, not only to 

 enable us more exactly to interpret the be- 

 havior of such animals but also, and par- 

 ticularly, for the light which it may throw 

 upon human visual processes. That ani- 

 mals have eyes might seem to imply that 

 they see colors and yet, as is weU known to 

 you, evidence is rapidly accumulating to 

 render it fairly certain that many animals 

 supposedly possessed of color vision, in 

 reality are sensitive only to differences in 

 brightness or luminosity. A careful ex- 

 amination of the retinae of such animals 

 may well give us our long needed clue 

 wherewith to untangle the puzzles of the 

 human color sense. In the case of man it 

 seems not unlikely that a completely ade- 

 quate color theory must await researches 

 in physiological chemistry as yet immade. 

 Nevertheless, we may get our start from 

 such investigations as these just suggested 

 upon the animal retina. 



I need hardly add that a correct interpre- 

 tation of animal behavior depends upon the 

 solution of problems such as these: for 

 example, much evidence is now at hand 

 indicating that animals may possess de- 

 veloped sense organs of whicTi they make 

 little or no actual use under normal condi- 

 tions. It is wholly problematic whether 

 certain birds make any actual use of smell 

 as a sense process, and yet the evidence 

 suggests that anatomically they are 

 equipped to respond to odors. Similarly, 



