CHAPTER VII. 



EFFECT OF ALCOHOL ON MOTOR COORDINATIONS. 

 GENERAL MOTOR PROCESSES. 



The motor side of our original program has suffered abbreviation 

 through our time limits more than any other in this research. The 

 program called for an investigation (1) of muscle threshold, (2) of motor 

 fatigue, (3) of muscle tremor, as well as (4) of the speed of movement. 

 Tentative experiments were made in all these directions. But only in 

 the fourth, which we came to interpret broadly as a measure of motor 

 coordination, did the available technique appear to warrant the inclu- 

 sion of the measurements in the regular series of experiments. 



(1) In our attempts to measure the muscle threshold we used the 

 Martin complex of apparatus as described in Chapter VI. Our first 

 difficulty was to make a satisfactory non-polarizable electrode of uni- 

 form surface contact and resistance. After experimenting with various 

 devices, we finally came to use the following relatively satisfactory 

 form: Prepared clay (clay moistened with normal salt solution) was 

 spread to a thickness of about 3 mm. on the bottom of a porous porce- 

 lain cup, which was about 2.5 cm. in diameter and about 2 cm. high. 

 An amalgamated zinc electrode wrapped in absorbent cotton which was 

 well moistened with saturated zinc-sulphate solution was placed inside 

 the cup. The clay-covered cup was placed against the appropriate 

 part of the skin, to the configuration of which it readily conformed, and 

 was held in position with an elastic band. With reasonable care this 

 arrangement provided an electrode of uniform size, even contact, and 

 quite regular resistance. As an indifferent electrode we used a fluid, 

 non-polarizable electrode, such as was used in the sensory-threshold 

 experiments. The significant electrode was regularly placed on a point 

 of the left forearm, which prehminary exploration snowed to be the 

 common point for the extension of the digits. A finger of the right 

 hand was inserted in the indifferent electrode. In this manner a 

 considerable body of data was collected which was too obviously faulty 

 to be included in this report. The faults depended, first, on the diffi- 

 culty in observing threshold contraction of the digital extensors. No 

 device which we adopted for registration seemed to work satisfactorily. 

 Observation of the muscle was sometimes more and sometimes less 

 satisfactory than observations of the movements of the fingers. Even 

 with the most favorable conditions for observations we were seldom 

 satisfied that we had a true threshold, either with increasing or with 

 decreasing stimuli. The area of uncertainty would frequently extend 

 over several millimeters of the inductorium scale. This was more 



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