CHAPTER VI. 



EFFECT OF ALCOHOL ON THE SENSORY THRESHOLD FOR FARADIC 

 STIMULATION (MARTIN MEASUREMENTS). 



In a series of papers published in the American Journal of Physiology 

 between the years 1908 and 1911, Professor E. G. Martin, 1 of the 

 Harvard Medical School, developed a method for measuring induction 

 shocks. Starting with a properly calibrated inductorium of standard 

 construction, it is now possible to include in a single equation all the 

 various physical factors which are involved in the production of an 

 induction shock of threshold intensity. The absolute threshold of a 

 tissue may be expressed in units which are directly comparable wherever 

 properly calibrated instruments are used. To these units Professor 

 Martin has given the name /3 units. Their use involves more experi- 

 mental data and considerably more mathematical elaboration of the 

 data than has previously been customary in measurements of threshold 

 for Faradic stimulation. The experimental procedure, however, is 

 simple and the mathematical work with Wilbur's 2 simplification of the 

 Martin equation is now neither difficult nor extravagantly time-con- 

 suming. For the theoretical derivation of the various formulae, we 

 must refer to Professor Martin's papers, especially to his book, "The 

 Measurement of Induction Shocks." 



We can scarcely overestimate the advantages to experimental psy- 

 chology of a sensory threshold technique in which the stimuli can be 

 expressed in absolute units of electrical energy. The high standards of 

 instrumental accuracy, the ease of manipulation, and general avail- 

 ability of electrical stimuli, the simplicity of the skin receptors, and 

 their freedom from complicated adjustments seem to make the thresh- 

 old for Faradic stimulation the simplest and most satisfactory sensory- 

 threshold measurements at our disposal. The recent criticisms of 

 inductorium calibration by Erlanger and Garrey 3 do not affect the 

 fundamental value of the method (Martin 4 ) . Like all threshold meas- 

 urements, however, in which one must depend on the verbal reports of 

 the subject, the Martin threshold probably depends for highest accu- 

 racy on the subject's training in observation. There is at present no 

 means for analyzing the sensory process, to determine in how far 

 apparent variations in the threshold of any particular subject depend 

 on changes in central conditions of perception, on interest, attention, 

 alertness, etc. Our experience suggests that some indicator for the 



'Martin, a. Am. Journ. Physiol., 1908, 22, p. 116. 



b. Am. Journ. Physiol., 1909, 24, p. 269. 



c. The Measurement of Induction Shocks, New York, N. Y., 1912. 

 2 Martin, Bigelow, and Wilbur, Am. Journ. Physiol., 1914, 33, p. 415. 

 3 Erlanp;er and Garrey, Am. Journ. Physiol., 1914, 35, p. 377. 



4 Martin, Am. Journ. Physiol., 1914-15, 36, p. 223. 



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