(. 113 ) 



intensify of the ciirroiil will at any uiomumiI he proiioi-lioiial l<» tlic 

 active electi'omotive force, so that the fniidanieiital difference between 

 the electrometer and tiie galvanoniofei- is no obstacle to a comparison 

 of both insfriiments. 



The strin»- <»alvanoniefer has sevei-al advantages over the capillary 

 electrometer. First tlie deflection of the string galvanometer will in 

 many cases and especially in the case of tracing a linman cardiogram 

 be greater and quicker than the deflection of the caj)illary electro- 

 meter. Then the ca[)illary electrometer is less accurate in the constancy 

 of its indications, their proportionality to the potential differences and 

 their equality in opposed directions. 



A highly magnified image of the mercnr}- meniscus cannot be so 

 sharply projected as that of a fine thread and one cannot regulate the 

 sensitiveness of the capillary electrometer to a predetermined amount. 

 The electrical insulation of the string galvanometer is much easier 

 than of the capillary electrometer and a phenomenon like "creeping" 

 does not occur with the galvanometer. 



In the capillary electrometer the movement of the meniscus is 

 damped by the friction of the mercury and sulphnric acid when 

 streaming through a narrow tube. Invisibly small traces of impu- 

 rities ma}^ hinder or even entirelj^ stop the movement of the mer- 

 cury meniscus. Many a capillary had after a relatixely short time to 

 be replaced by a new one because there was a "hitch" in the 

 movement of the meniscus. In the string galvanometer, on the 

 other hand, we have air-damping as well as electromagnetic tlamping, 

 l)oth of which work with perfect regularity. The electromagnetic 

 damping can moreover be varied at will by changing the intensity 

 of the field and the resistance in the galvanometer circuit. 



Plate II contains the electrocardiograms of some six persons, traced 

 by means of the string galvanometer. In the coordinate system an 

 absciss of one millimetre has a value of 0.04 sec, while an ordinate 

 of one mm. represents a P.I), of lO^"* Volts. By choosing these round 

 numbers the curves satisfy generally the requirements of the inter- 

 national committee for the unification of physiological methods. 



The movement of the (jiiartz thread, as may be seen from the 

 normal curves at the end of each photogram, was dead-beat and very 

 quick, so that the traced electrocardiogram is a fair representation ot 

 the oscillations in the potential difference existing between the right 

 and left hands of the ex|)eriinenlal person. As a rule this may be 

 admitted for the lower tops P, (2, S and T without any noticeable 

 error. l>ut for (he high and shai-p top R a correction should be 

 applied especially in pholograms 8 and 9, a correction l)y which 



8* 



