266 PHYSIOLOGY. 



"breaking" of the current; but the muscle ordinarily re- 

 mains inactive while the current is passing. 



Induction Current used in Physiological Experiment. The in- 

 terrupted current, or induction current, is therefore commonly employed 

 as a stimulus in physiological experiment. A sudden change seems 

 to be requisite for producing the nerve impulse necessary to rouse 

 a sensation in ordinary circumstances. Pressure may be applied so 

 gradually that we fail to notice it. The art of the pickpocket, of the 

 ventriloquist, of the sleight-of-hand performer, depends largely on this 

 fact. Attention is called to something else, and the work is either 

 quickly done when attention is completely absorbed on something else, 

 or the act is so gradual that no sudden change is noted. In smelling 

 it is often necessary to sniff; the sudden rush of particles of air bearing 

 the odorous particles against the surface bearing the nerve endings 

 seems to be necessary. 



Dreams. Dreams, due to more or less perfect brain activity, are 

 often traceable to nerve impulses brought from the digestive tract, from 

 the respiratory organs, from the skin (heat and cold and pressure), 

 from sound, from any internal organ, according to the condition of the 

 blood, pressure, etc. It seems to be well settled that dreams seeming 

 to cover long periods of time really take place in a very short space of 

 time, just as sometimes during waking hours thoughts fly through the 

 mind in countless numbers and with incredible swiftness. 



Ignoring Nerve Currents. Do we have dreams when we recall 

 none? Without attempting to answer this question it is well to note 

 that the brain undoubtedly is constantly receiving nerve currents to 

 which it pays no heed, or at least of which we are not conscious. 

 For instance, our clothing is touching nearly the whole of the surface 

 of our bodies, and, plainly, the surfaces thus touched are affected. 

 Undoubtedly currents go to the brain, but as they are of no significance 

 in ordinary circumstances, we learn to disregard them. If a savage 

 were suddenly clothed as fully as we are, he would, for a long time, 

 be continually conscious of the fact. 



Judgment. In what is called Aristotle's experiment, 

 the experimenter crosses the first and second finger, and 

 feels an object with the fingers thus crossed and eyes shut. 



