INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 395 



this movement could not take place. Again, some rats require 

 the cumulative effect of one or more daily trials of 30 minutes 

 each before the latch is raised. In such rats, movements are at 

 the beginning of a trial or trials actively performed. Reflex ex- 

 citability persists only a part of the 30 minutes and appears 

 almost absent at the end of this period. For such animals, a 

 greater time is required before certain responses are made, and 

 organic changes occur, before the neck reflex really appears. 

 And if these changes do not actively take place the problem re- 

 mains unsolved. Previous responses and organic changes have 

 little effect in eventually producing the neck reflex when the 

 rat's muzzle touches the latch, or even when it is moved part way 

 out of the notch. With such rats, it appears, reflex excitability 

 with concomitant organic changes is to a great extent absent, 

 and the changes that do take place do not fit the rat for the 

 attainment of posture for the solution of the problem. 



It can be determined experimentally that the cumulative effect 

 of all movements with organic changes is a necessary condition 

 for the production of the neck reflex movement, but this consti- 

 tutes an additional problem for investigation. The effects that 

 are produced can be shown and then judged by the number of 

 times the latch is touched before the neck reflex is produced. 

 The number of times the under surface of the latch was touched 

 by the rat's head or muzzle was recorded on the smoked-drum 

 of a kymograph. A light spring with electric contacts in circuit 

 with a signal magnet was placed on the under surface of the 

 latch. Records of 6 different litters are given in table 1. The 

 positive sign in this table indicates that the muzzle of the rat 

 touched the latch one or more times in immediate succession or 

 at different times on that trial or day. The negative sign indi- 

 cates no touches; the letter M, that the latch was moved part way 

 out of the notch; and the letter S indicates the solution of the 

 problem. 



When a solution of the problem occurred, usually one or more 

 touches of the muzzle were recorded before the neck reflex move- 

 ment was produced to raise the latch. In some instances, though 

 very rarely, the first touch of the latch resulted in the production 



