656 O. D. ANDERSON 



In order to make the conditioned motor and the condi- 

 tioned salivary reflexes quantitatively comparable, it was 

 necessary that some measurement of the motor reflex be 

 used. The height to which the forepaw was raised at each 

 flexion of the limb was measured and summated automatically 

 during the standard 10 second period of stimulation. During 

 this interval, the limb to which the electrode was attached 

 would, in some cases, be flexed three or four times, the foot 

 being raised each time 5 or 6 inches from the platform. This 

 type reaction we had previously termed "weak." In other 

 cases, the limb would be flexed eight or ten times during the 

 same period, the foot being raised 10 inches or more each 

 time. This reaction was considered "strong." To bring these 

 descriptions to numerical terms we used a modification of 

 Fick's work accumulator, the ratchet wheel and pawl shown 

 in figure 3 of plate 107. This device is so arranged that it 

 registers in millimeters the reduced height of each flexion 

 of the limb and thus gives the total value for the magnitude 

 of successive flexions occurring during the standard time. 

 The "weak" reaction may thus register only 100 mm, while 

 the "strong" may have a magnitude of 300 mm or more. 

 This method has been used over a period of 8 years for both 

 the sheep and dog and has proved entirely accurate. It is of 

 great value not only in providing means for comparing the 

 values of the reflexes found in one animal with those found 

 in another, but also in providing an accurate way of studying 

 the comparative values of the reflexes in the same animal 

 over long periods of time and during natural and experi- 

 mental alterations of the animal's physiological state. 



In order to provide further kinds of behavior before and 

 after the critical procedure, most of the animals were tested 

 for their ability to discriminate between two similar stimuli. 

 The problem presented was that of distinguishing between 

 a fast and a slow rate of the beating metronome. The rate 

 of 120 beats per minute was always reinforced by food or 

 by shock, as the case may be, while the rate of 28 beats 

 (sometimes 42 beats) was never followed by the food or shock. 



