492 JOHN LINCK ULRICH 



points. This makes the curve very irregular in outline. The 

 descending points represent the fact that directive integration 

 is difficult to establish because of fluctuations in the extensor 

 thrusts. Any descending point not representing a perfect 

 record, indicates that imperfect responses or ineffective extensor 

 thrusts are made before the plane without a change in the posi- 

 tion of the rat. When a high altitudinal point is reached and 

 directive integration is facilitated for any trial, ineffective re- 

 sponses are made before the plane, and a change in position- 

 that is progression from the plane and a return later to the 

 plane, occur. A very high altitudinal point may also mean 

 repeated advances to the plane took place. When directive 

 integration is facilitated, and interaction of body parts is devel- 

 oped, then perfect records for several consecutive trials are pro- 

 duced. Then greater and lesser upslopes and downslopes 

 appear, and they can be said to be due to slight decreases in 

 reflex tone or to other changes in the rat. When marked fluc- 

 tuations in the coordination of extension and flexion of the limbs 

 occur, then the imperfect responses that are produced increase 

 the altitudinal points, that is, a great upslope appears. 



Curve II, was constructed from a rat's record presented in 

 table 13. The rat whose record is given in this table possessed 

 undeveloped reflex thrusts, and manifested in the early trials of 

 learning hyponormal reflex excitability. There exists on this 

 curve from the first and the second trials, high altitudinal points 

 and as marked descending points in the next few trials. When 

 directive integration is facilitated and reflex excitability mani- 

 fest, points in the curve are closer to the abscissa. At this time 

 the method used to plunge the plane that is running and step- 

 ping on the plane has become fairly constant. Of the 60 trials 

 given only 3 perfect trials are recorded. All upslopes in this 

 curve indicate that the method used was at times more effective, 

 yet rarely leading to the production of perfect trials. When the 

 results obtained are measured with those of preceding rats, it is 

 clear that only partial interaction, because of the existence of 

 undeveloped reflex mechanisms, is possible. The delineation 

 of this curve reveals this inadequate interaction of parts for 

 learning. 



