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CONTRIBUTIONS TO PHYSIOLOGICAL TECHNIQUE. 



By F. S. Locke. 



(Received for publication 28th August 1908.) 



I. Signalling more than one Kind of Event with only one 

 Writing-Lever. 



When events of more than one kind have to be graphically recorded 

 electrically, it is usual to employ a separate electromagnetic signal for each 

 kind of event. The proper arrangement of more than one electric signal in 

 relation to the other recording apparatus is often a matter of irritating 

 difficulty, when they do not form a permanent fixture on the kymograph 

 employed (Hering-Rothe, Brodie-Palmer), and even here the limited 

 adjustability of the signals in height renders the application of another 

 system of signals frequently desirable. Combinations of two or more 

 signals on one supporting rod suitable for use on any recording surface have 

 been designed (Carl Ludwig, Langendorff, and others), but at best the 

 multiplication of writing-points is not a thing to be wished for, and in many 

 cases it is of distinct advantage to be able to make one writing-point 

 record distinguishably in addition to time-intervals at least one other kind 

 of event. I have devised two ways whereby this end is attained, one of 

 which demands an electromagnetic signal of special construction, while the 

 other, although necessitating more complicated electrical connections, can be 

 used with any signal possessing an adjustable armature-spring and iron 

 cores not exhibiting too much hysteresis. 



A Double Electromagnetic Signal with a Single Writing-Lever. 



The signal in question consists of two electrically separate electro- 

 magnets, the armature of each of which, instead of being connected with a 

 separate recording lever, is connected with one common recording lever by 

 means of a flexure joint which serves either as point of application to the 

 lever of the force of attraction of its own electromagnet, or as relatively 

 fixed axis of rotation of the lever when acted on by the force of attraction 

 of the other electromagnet, the movement of the writing-point attached to 

 one end of the lever being in opposite directions in the two cases. The actual 

 mode of construction is shown in fig. 1, and is so obvious that a detailed 

 description is unnecessary. The special points worthy of mention are : — 



(]) The armature-springs, by which the armatures are connected with 

 the solid brass frame of the apparatus, are of sheet phosphor-bronze, of 



