406 v MENTAL FUNCTION 



complexes given somehow wholly or in part through the sensory end- 

 organs. One has to. think of this process of fusion as almost the chief 

 underlying activity of consciousness. As to its means, nothing is known. 

 We see anatomically discrete sense-organs and other protoplasmic units 

 we experience in ourselves the products of their fusion. No present 

 facts or theories satisfactorily bridge this gap in our understanding of our 

 consciousness. Unsupported hypothesis is not enough in science, else 

 we might perhaps attempt a solution of the problem by supposing that 

 it is the general body-protoplasm which represents consciousness rather 

 than the nervous system (including its disparate sense-organs) alone. 



The various degrees of activity of the sense-organs in the body imply 

 many degrees in the intensity of the sensations they represent. Each 

 sense has a range of intensities from the threshold to that at which no 

 further increase of sensation is possible and the sense-organ is injured. 

 But what of the effects produced by stimuli below the threshold-intensity? 

 In the case of a frog's gastrocnemius muscle, it will be seen, on reference 

 to the laboratory experiments (No. 45) in the Appendix, that there exists 

 a summation in stimuli which singly are inadequate to produce a con- 

 traction. In other words, if the threshold-stimulus of a muscle be found 

 and then stimuli of less intensity be repeatedly thrown into the muscle 

 a few seconds apart, contraction finally occurs. The slight stimuli do 

 then influence the muscle and leave traces in it which summate and after 

 a while reach the threshold- value and occasion a contraction. One sees 

 the same thing in the sensory realm. It is, for example, an almost 

 universal human habit to knock repeatedly rather than once on a door 

 when one would attract the attention of those within, in part on this 

 same principle of summation. Stimuli, then, below the threshold do 

 affect the organism's protoplasm, and leave some sort of an impression 

 more or less persistent. This fact, as we have seen, is easily proved by 

 actual experiment, and so proved becomes the basis of an important 

 principle in the relations of the stimulus to the reaction both psychical 

 and somatic. It leads to an understanding, in a way, of the far-reaching 

 phenomena of the "sub-conscious" aspects of the mental process. 



In a text-book of physiology we need not be concerned even for a 

 moment with that interesting but futile scholastic doubt whether a 

 sensation, an aspect of consciousness, can be said ever to be unconscious. 

 We cut the doubt promptly here, as in the chapter on the senses, by the 

 fourfold assertion that it is a matter only of terminology; that "sensa- 

 tion" is not in all cases an accurate term, in so far as it usually implies 

 conscious experience; that there are all degrees of consciousness, the 

 lesser degrees merging into (neural?) influences which singly have no 

 consciousness capable of being felt; and finally that these subconscious 

 influences constitute the place, the time, and the means wherein the 

 mental process fuses into the other processes which physiology describes. 

 What these influences or impulses or conditions of activity are and 

 where they originate we do not know completely. We think we know 

 that the neural maze is their pathway through the body. We suppose 



