March 10, 1899.] 



SCIENCE, 



Til 



meriting' leaves revealed the absence of ex- 

 tended bacterial colonies, the presenc of which 

 were naturally to be expected if bacteria were 

 the cause of the phenomena in question. The 

 true cause, I have recently established beyond 

 a doubt, is the presence of two kinds of oxi- 

 dizing enzymes in the tobacco leaves. As soon 

 as the Bulletin describing these investigations 

 is published a full review will be given in this 

 Journal. 



Oscar Loew. 

 Division of Vegetable Physiology and Pa- 

 thology, U. S. Dept. of Agriculture. 



THE anesthetic EFFECTS OF A SINUSOIDAL CUR- 

 RENT OF HIGH FREQUENCY. 



To THE Editor of Science : In your issue 

 of June 3, 1898^ I had the honor of communi- 

 cating an observation on the anaesthetic eflfects 

 of a sinusoidal current of high frequency. I 

 take the liberty of sending you the following 

 further observations. 



a. The anesthetic effect may be produced 

 by sending the current longitudinally along the 

 the nerve. Thus, a current sent along one of 

 the nerves of the arm can be used to produce 

 anaesthesia in parts of the arm supplied by it. 

 With a pleasant current of about 28,000 alter- 

 nations per second passing between the elbow 

 and the hand, a needle can be painlessly run 

 into the forearm. 



b. At the suggestion of Professor B. Moore, 

 of the Yale Medical School, I applied the cur- 

 rent to the tongue, with a view to testing the 

 theory that the sensation of taste may be due 

 to vibratory stimuli. If the theory were 

 true the fluctuations in the sinusoidal current 

 might be expected to produce sensations of taste 

 of various kinds. The experiment showed that 

 fluctuations up to about 29,000 complete periods 

 per second produce no sensations of taste what- 

 ever ; the only sensation is that of tickling and 

 puckering. 



c. It should perhaps have been stated in my 

 original communication that the main purpose 

 of the investigations with the sinusoidal current 

 was to determine the various sensations at 

 different frequencies. They have been deter- 

 mined for two subjects as follows : (1) Thresh- 

 old of sensation of touch at a frequency of about 



480 complete alternations per second ; (2) 

 threshold of disagreeableness at about 840 ; (3) 

 threshold of pain at about 960 ; (4) disappear- 

 ance of pain at about 1,440, followed by a pe- 

 culiar, agreeable sensation ; (5) disappearance 

 of agreeableness at a point not yet determined, 

 followed by a faint sensation ; (6) disappear- 

 ance of sensation at a point not yet determined. 

 For constant conditions these figures are quite 

 constant, the probable error ranging from y^j of 

 1 /o to 4 /(. . 



d. Applying the electrodes to the nerves of 

 the arm in a way to move the muscles of the 

 forearm and hand I find a similar neuro- 

 muscular effect. As the current rises in fre- 

 quency from zero the muscles contract steadily 

 up to a certain point, after which they gradu- 

 ally relax. The process is the same when we 

 start with a high frequency and descend to 

 zero. The phenomenon can hardly be due to a 

 diminished intensity of the high-frequency 

 current. 



e. It may be added that the instrument used 

 is a Kennelly alternator run at a very high 

 speed. Similar high-frequency machines have 

 been used by Nikola Tesla, who has not re- 

 corded any of the above phenomena ; possibly 

 his machines do not produce sinusoidal currents. 



/. Using another machine which simply in- 

 terrupted a galvanic current up to 100,000 

 times per second I find that above a certain 

 point (not yet measured) the interruptions 

 cease to have any effect other than merely re- 

 ducing the strength of the current when it is 

 sent through the tissues. 



E. W. Scripture. 



Yale University, New Haven, Conn., 

 February 28, 1899. 



NOTES ON PHYSICS. 

 THE METRIC SYSTEM. 



The Hartford Steam Boiler, Inspection and 

 Insurance Company of Hartford, Conn., has 

 issued a very neat and convenient volume, of 

 ' pocket size,' containing tables for the Conver- 

 sion of English weights and measures into their 

 metric equivalents, and vice versa. It opens 

 with a very interesting discussion of the metric 

 system, which lacks, however, any recognition 

 of the International Bureau of Weights and 



