46 KNIGHT DUNLAP 



(whence the term "drainage"), so that a transit a'-b is actually 

 established at the moment, but this need not be assumed. The 

 important fact is that a condition of functional connection is es- 

 tablished so that at the next occurrence of a centripetal discharge 

 from a' there will be a tendency for an arc from a' to b to be actu- 

 alized: and if the process be repeated several times the arc will 

 certainly be established, and the stimulation of a 1 will produce 

 the movement b through the direct transit a'-b, with no need of 

 the sensory processes B' at all. 



The linking together of 6 and c, representing the second and 

 third steps in the waltz; and the linking of the third and fourth, 

 fourth and fifth, and fifth and sixth; follow the same course as the 

 linking of a and b. Eventually, the series is so completely asso- 

 ciated that given the proper start, it will continue with no neces- 

 sary further stimulations than those supplied by the muscular 

 contractions themselves. And this result follows from the gen- 

 eral properties of neurons as assumed under the concepts of in- 

 tegration and drainage, needing no special "association centers," 

 or of any groups of nerve cells possessing functional properties 

 differing in any way from the properties of all nerve cells (except- 

 ing in so far as receptors may constitute such a class). 



Obviously, the first connections of the afferent and the efferent 

 parts of the circuits from muscle to muscle will be established in 

 that part of the central nervous system in which the synaptic 

 contacts are most numerous and complicated, namely, the cere- 

 brum: the great central automatic switch board. 



It is not to be supposed that during the fixing and perfecting of 

 the habit by continued practice changes in the route of the cir- 

 cuit do not occur. Possibly the circuit as first established is 

 later very much shortened; possibly some circuits are so short- 

 ened and modified that when the habit is perfected the route no 

 longer passes through the cerebrum. On these points there is 

 little information available. 



The "proper start" above specified as the prerequisite for the 

 operation of the completed habit must not be simply conceived. 

 The mere completion of the first step in the waltz series is not a 

 sufficient "sfart" for that series: if it were, an expert waltzer 



