THE NERVOUS SYSTEM OF MAN. 6l 



on the stomach, heart, etc. In other cases, as in swal- 

 lowing, sneezing, coughing, breathing, etc., the current 

 short circuits, indeed, and appropriate motion takes 

 place immediately by reflex, but sufficient overflow 

 reaches the cerebrum to produce consciousness. In 

 ordinary cases of impression on an external consciously 

 sensitive surface or sense organ, as already seen, the cur- 

 rent passes on without short circuit directly to the cere- 

 brum, and consciousness takes charge of the response; 

 but if the impression be painful, then the current short 

 circuits without waiting for the slower action of the 

 cerebral system. 



For simplicity's sake we have represented the connec- 

 tion throughout as physical and continuous; but, as 

 already explained (Fig. 21, page 37, Fig. 28, page 42), 

 the connection between neurones is probably by touch- 

 ing fingers or interlacing dendrites. It has been sug- 

 gested that the fingerlike extensions are like pseudopods 

 of amoebae — that by extension and contraction they make 

 and break contact with one another. In the active wak- 

 ing state they elongate and make contact; in uncon- 

 sciousness, in coma, and in sleep they contract and break 

 contact. On this view disconnection of neurones is the 

 physical cause of sleep.* 



Illustration by Telegraphy. — To enforce these princi- 

 ples still further and make them still clearer we make a 

 somewhat elaborate comparison with a system of teleg- 

 raphy. 



Suppose, then, the Capitol at Washington represents 

 the head. In it there is a great rotunda; this represents 

 the cerebrum. Suppose all about the walls a series of 

 alcoves; these shall be the convolutions. These are, say, 

 full of battery cells ; these are the sensory and motor 



* Mathias Duval, Rev. Sci., lx, 321, 189S. 



