( 107 ) 



witli mellivlalcoliol. 'I'Iiis iniiiiiiiimi is nol prcsciil in ihe lii.iilici- 

 coiiceiitratioiis but at the largei- dilutions it boconics more and more 

 evident. This minimum is found precisely in the neighl)oui"liood of 

 those dilutions {p = 22 and higher) at which Lohry dk Hruvn and 

 Steokr and Lulofs have worked in the ex])erimenls refci-red lo 

 above and the amount of water in the alcohol is also the same as 

 that for which these investigators have found the maximum of 

 reaction velocit}-, namely in 60 to 80 per cent alcohol. There is 

 therefore parallelism between the two phenomena; for melliyl alcoliol 

 -|- water -|- sodium a maximum of the reaction velocity corresponds 

 with a minimum of conductivity. 



The experiments are being continued up to piu-e ll.,() and also 

 extended to mixtures of ethyl- and methylalcohol. 



Amstenhmi, June 1903. Org. Chem. Lab. University. 



Physiology. — Tlie string galvanometer and the Jiuman electro- 

 cardiogram. By Professor W. Einthoven. (Physiological labo- 

 ratory at Ley den.) 



In the Bosscha-celebration volume of the "Archives Néerlandaises" ') 

 the principle of a new galvanometer w\as mentioned and the theory 

 of the instrument dealt with. The practical usefubiess of the instrument 

 especially for electrophysiological measurements may be judged from 

 what follows. 



It may be remembered that the instrument consists principally of 

 a silvered quartz thread which is stretched like a string in a sfrong 

 magnetic field. When an electric current is passed through the thread, 

 this latter deflects perpendicularly to the direction of the magnetic 

 lines of force and the amount of the deflection can directly be meas- 

 ured by means of a microscope -with an eye-piece mici'ometer. 



What is the sensitiveness that can be obtained in this maimer? 



Since the above-mentioned publication a number of material impro- 

 vements have been made in the instrument by which it is possible, 

 for instance, to give a very feeble tension lo the string, now a quartz 

 thread 2.4 ft thick, with a resistance of 10 000 Ohms. If the tension 

 is so regulated that a deflection takes place in from 10 to 15 seconds 

 depending on its amount, every millimetre of the displacement of 

 the image of the string corresponds to a current of 10— " Amp. when 

 a 660-fold magnification is used. As under these circumstances a 



^) W. Einthoven. Un nouveau galvanomètre. Archives Nécrlaudaiscs des sciences 

 exactes et naturelles. Sér. II. Tome VI. p. 6:25. 1901. 



