June 22, 1917] 



SCIENCE 



625 



of exciting action ratlier than organs of an 

 informing nature. It must also not be for- 

 gotten that though the sense organs of the 

 higher animals are in many cases primarily 

 organs of information, so to speak, they 

 probably all still retain their original func- 

 tion of exciting muscles, at least indirectly, 

 to action. They are the beginnings of prac- 

 tically all reflex arcs. Not only is this true, 

 but not a few of them retain, so far as our 

 conscious Hfe is concerned, much of that 

 hidden and submerged state that character- 

 izes them in the lower animals. They lie in 

 their activities below the conscious and even 

 the subconscious level. This can be exem- 

 plified in one of the senses already named, 

 the muscle sense. We are almost continu- 

 ously cognizant of light, noise, smell and 

 so forth, but we find it almost impossible to 

 realize in our conscious states sensations 

 from the muscle sense. Obscure, vague and 

 indefinite, they impress us scarcely at all. 

 Only here and there do they appear to rise 

 into the region of strong sensation. Within 

 the last few years it has been shown that 

 the sensation of hunger is dependent upon 

 stomach movements. Each hunger pang is 

 due to a wave of muscular contraction pass- 

 ing over the walls of the stomach. It is, 

 therefore, not improbable that the hunger 

 pang is a muscle sensation that, from its or- 

 ganic importance, has lifted itself from the 

 low level of unconscious activity into the 

 higher strata of our conscious states. 



The great majority of the sense organs of 

 the lower animals are concerned with yield- 

 ing impulses to motion that are in no way 

 associated with consciousness, and this is 

 undoubtedly their primitive function. 

 Such animals often exhibit complicated sys- 

 tems of transmission tracts connecting their 

 sense organs with their muscles, and these 

 tracts collectively mark the beginning of a 

 central nervous system. It is probable that 

 a sensory equipment of this kind, with the 



well-established beginnings of a central 

 apparatus, afforded the necessary settings 

 for the appearance of consciousness, which 

 thus found roughed out by the earlier neces- 

 sities of the organism a system of sensory 

 and centi-al components capable of sustain- 

 ing future growth. At this stage the sense 

 organ must have added to its primitive 

 function of calling forth muscle activity 

 that of supplying messages to a growing 

 central organ, a function that has become of 

 such paramount importance in man. 



If this outline of the sources of our ner- 

 vous activity is true, it follows that any 

 conception of the nervous system that as- 

 sumes sensation as a basal phenomenon is 

 most assuredly to be abandoned. Sensa- 

 tions are associated with only the later 

 phases of nervous development. The fea- 

 ture that has been present throughout the 

 whole period of this evolution is muscular 

 activity. In fact, as I have already stated, 

 we have reason to believe that muscular ac- 

 tivity preceded nervous origins and that 

 nervous tissue appeared in consequence of 

 the presence of muscles. Our own sensa- 

 tions, then, are not our most fundamental 

 and primitive nervous processes, but behind 

 these and of much more ancient lineage are 

 our impulses to action, our wishes, our de- 

 sires, and the whole vague body of nervous 

 states that drive us to do things. These are 

 the most ancient and deeply seated of our 

 nervous propensities, and immeasurably 

 antedate in point of origin, our sensations 

 with all that supergrowth that constitutes 

 the fabric of our mental life. We do well 

 to warn ourselves to think before we act. 

 Action is the oldest and most ingrained of 

 our nervous functions, thinking the newest. 



You will pardon me if I have led you 

 from the realm of simple fact and observa- 

 tion far afield into that of pure speculation, 

 for the general scheme of the sources of our 

 nervous action that I have outlined must be 



