144 PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



Zr is the value of Z at skin resistance. 



R is the skin resistance. 



Zr' is the value of Z when the arbitrary known resistance is introduced 

 into the primary circuit. 



R' is the total value of the skin and known resistance. 



As appears from the above formulae, the Z values take no account of 

 the changing skin or electrode resistance. Since these changes in the 

 course of our 3-hour experiments were never large, and since Martin 

 had already shown that Z and j8 values tend to run a parallel course, it 

 is probable that no great violence has been done to the results by 

 computing the effects of alcohol from Z. This course was necessary 

 in the present instance, because measurements of skin-resistance which 

 we made before December 23 were technically unreliable, and in several 

 instances these earlier measurements of Z were the only ones available 

 as a first normal day. 



The general effects of alcohol, doses A and B, are tabulated for each 

 subject in the summary (table 23), in both absolute differences and in 

 percentile changes. Inspection of table 23 shows that for both normal 

 and alcohol days, the value of Z in succeeding series of the same day 

 tends to rise. In psychological terms the sensory threshold rises or the 

 sensitivity decreases as the experimental periods of 3 hours progressed. 

 There is, however, a distinct difference between normal and alcohol 

 days in this respect. On alcohol days the sensitivity decreases more 

 than on the normal. 



The tendency of the threshold to rise during a normal experimental 

 period is practically explained by the interaction of the daily rhythm. 

 Since most of the measurements here reported were made in the after- 

 noon between 3 and 7, one would expect such a tendency as a result of 

 the daily rhythm which was described by Grabfield and Martin. 1 



But our experimental conditions were not strictly analogous to those 

 of Grabfield and Martin. In their case, the experimental measurement 

 of the Faradic threshold was introduced as an interruption to some 

 regular work. In our case, the 3-hour series of measurements permitted 

 only the most restricted activity of the subject. Such pronounced 

 neuro-muscular relaxation as our pulse-records show at the end of the 

 period was probably not duplicated in their experiments. It is still 

 more significant that in spite of quickened heart-rate, the effect of 

 alcohol is still further to decrease sensitivity. 



The last two columns of table 23 show the percentile value of this 

 difference for the main group of subjects; it averages 21 per cent of the 

 average normal value of Z, after the ingestion of the smaller dose of 

 alcohol, and 8 per cent after the ingestion of the larger dose. On the 

 basis of our statistical theory, the one exception under dose A, Subject 



Grabfield and Martin, Am. Journ. Physiol., 1912-13, 31, p. 300. 



