November 8, 1894] 



NATURE 



43 



set in action, and the water repeatedly shaken. A flask of 

 cooled sulphuric acid was also put into communication with the 

 evacuated enclosure to absorb water vapour, and thus proniote 

 partial distillation of the water. When dissolved gases had 

 been removed, the vertical tube was sealed, and water was then 

 distilled from the bulb into the receiver, the former being im- 

 mersed in a bath at a temperature of 30° to 40°, and the latter 

 in a cooling mixture at from o' to -8', the temperature being 

 kept as low as possible in order to diminish the solvent action 

 of water on the glass. The value obtained in this way for the 

 conductivity at iS' was o'25, or a number which is practically 

 only one-thiid of that given by water distilled in air. 



Small as this number was, it was not supposed to represent 

 the actual conductivity of water, because experiment showed 

 that the conductivity altered rapidly with the time, owing to the 

 dissoluiion by the water of material from the glass receiver, and 

 from the electrodes. The correctness of this supposition is 

 strikingly verified in a communication recently made by 

 Kohlransch and Heydweiller to the Berlin Academy of 

 Sciences {Silzun^iberichls, March 1S94). One of the pieces 

 of apparatus used in 1SS4, and described above, had been 

 allowed to stand filled with water for some ten years, and, 

 apparently from long coniact with the water, the glass has 

 become much less soluble than it is under ordinary circum- 

 stances. Indeed, during the time necessary for an observation 

 the conductivity does not alter appreciably, and onl^ rises by 

 O'oi in a day. The method of experiment employed is similar 

 to that just described, the main modifications consisting in 

 additional precautions to obtain the water air-free, and in 

 freezing the purified water nrior to its introduction into the 

 apparatus. This method of freezing, suggested first by Nernst, 

 is of value in eliminating volatile impurities which might distil 

 over wi'h the steam. The smallest value now found for the 

 conductivity is '0404 at iS°, or a number which is only i/20ooth 

 of the original value given by Pouillet, and only one-sixth of 

 that obtained in the satue apparatus in 18S4. 



Since with eacli improvement the value for the conductivity 

 has been largely reduced, the question which naturally arises 

 in connection with this last result is, how closely can it be sup- 

 posed to approximate to the truth ? Indeed, seeing that the 

 conductivity is so very small, it might fairly be suspected that 

 absolutely puie water is itself a non-conductor, and that the 

 observed conductivity is merely due to the presence of a slight 

 trace of impurity. As it seems almost itnpo-sible to answer this 

 question by purely expeiimenial methods, theoretical ails have 

 to be employed, and by means of the hypotheses involved in the 

 new theory of solutions, Kohlrausch and Heydweiller proceed 

 to show that pure water is actually a conductor, and that its 

 conductivity can be ascertained from their observations. The 

 method they employ is briefly as follows: — .\ccording to Art- 

 henius, if water is a conductor, the leason for this is that certain 

 of its molecules exist dissociated into the ions li and OH. 

 Moreover, the magnitude of the conduciivity depends upon two 

 factors : firstly, on the number of dissociated molecules ; and 

 secondly, on the velocities with which the ions travel. The 

 conductivity varies with the temperature becaue the number of 

 dissociated molecules, as well as the ionic velocities, increases 

 with the temperatuce. Krom these theoretical views, although it 

 is not possible to estimate the actual value of the conductivity, yet 

 the rate at which it should vary with the temperaiuie may he 

 ascertained. For, in the first place, according to van'i HolT, 

 the extent of the dissociation should vary with the temperature 

 just as it does in a dissociating gaseous system ; and in the 

 second place, the velocities of the ions II and OH may readily 

 be obtained at different temperatures from measurements on 

 dilute aqueous solution-, such as those of KOH, IICl, and 

 KCl. 



Now, Kohlrausch and Heydweiller measured at 18° the tem- 

 perature-rate of change for a series rf samples of water of 

 different degrees of purity, and also the conductivity of two 

 samples of very pure water at temperatures between - 2'' and 

 50°. They then assumed that the observed conductivity was 

 really a sum, being composed of the conductivities of pure water 

 and a dissolved impurity. They were thus enabled to show 

 how it is possible, by making use of the rate of change as 

 deduced by theory for the single temperature of iS°, to obtain 

 from their observations theconductivity of pure water at dilTerent 

 temperatures. 



The first result arrived at, is that the temperature- function of 

 Ihe conductivity over the entire range from - 2° to 50' agrees 



NO. 1306, VOL 51] 



within the limits of the experimental errors with the function 

 predicted by theory. This, as the authors remark, is one of 

 the most remarkable confirmations yet adduceil of the validity 

 of the hypothesis of the new theory of solutions. The second 

 and the most important conclusion for the question under 

 discussion is, that at 18° the conductivity of pure water has 

 in all probability the v.ilue 00361. The smallest value 

 actually observed, it will be remembered, was 0^0404. The 

 impurity present in the sample affected the conductivity, 

 therefore, by o'oo43, or by some 10 per cent. If this 

 impurity were of the nature of a salt, as in all likelihood 

 it is, the amount which would exert this effect would not 

 require to be more than a few thousandths of a milligram per 

 litre. We have here, therefore, the remarkable result 

 that an impurity of this nature, if present to the extent of 

 only a few parts per thousand million, is capaVjle of influencing 

 the conductivity by as much as 10 per cent, of its value. This, 

 together with what has already been said, leaves little question 

 that of all the physical constants of water, there is none which 

 is so sensitive to small traces of dissolved impurity as its electric 

 conductivity. J. W. Rodger. 



NEO-VITALISM}- 



\ QU-\RTER of a century ago, du Bois-Reymond headed 

 "^ the revolt of Mechanicalist Biology against the Vitalism 

 of Johannes Miiller. From Bichat to Magendie, from Johannes 

 MUUer to Schwann, the pendulum swung backwards and for- 

 wards ; but it was reserved for du Bois-Reymond, in his now 

 famous Berlin addresses, together with Ludwig and Helmholtz, 

 to expose the fallacies of vitalism, and establish physiol ogy on 

 a mechanical basis. 



In the present address he takes up arms against the "new 

 vitalism," which since the discoveries of Heidenhain r/ activity 

 of cell in secretion -Jenus mere mechanical diffusion, has made 

 a new departure, based on a partial misconception of these 

 secretory activities. The position of the debate as it now stands 

 will be best shown by an abstract of Prof, du Bois-Reymond's 

 recent manifesto. 



From Descartes and Leibnitz, until they encountered their 

 first opponent in Magendie, vitalistic theories were paramount. 

 During this period "vital force" was conceived as the attribute 

 of the sou! ill distinction to the body, or confused with the so- 

 called *' nervous principle," with animal heat or electricity. 



Johannes Miillerand .Schwann again fought out the question ; 

 even the discovery by Schwann of independent cell-life in the 

 organism failing to convince MuUer that his views were 

 erroneous. The overthrow of vitalism was reserved for Ludwig, 

 whose autographic methods strengthened the physical side of 

 experimental physiology. He came forward as the champion 

 of anti-vitalism, and tlie same position was taken up by many 

 of Muller's immediate pupils. The fundamental dilference 

 between this and aU previous criticism lay in the physico-mathe- 

 maiical training of the antagonists, which enabled them to 

 delect the Trfonov <1>eCSos of vitalism. This prime error is 

 the misconception of '* force." Force is not an entity existing 

 apart from matter ; it is ultimately a mathematical concept, 

 standing for the physical changes which alone can be known 'o 

 us. The atoms are not a truck to which the forces can be 

 harnessed ; their attributes are eternal, integral, inalienable. 

 Helmholtz said that without a rational conception of nature, 

 scientific research would have no meaning ; vital force, how- 

 ever, is unthinkable. 



The fundamental distinction between organic and inorganic 

 bodies has not been adequately recognised. In crystals, and 

 dead bodies generally, matter is in static equilibrium, stable, 

 indifferent, or labile ; in living organisms, tr.e equilibrium is 

 dynamic. As in heat, .and electrical diffusion, ihe rise and fall 

 ol current is balanced ; there is constant metabolism. And 

 metabolism, as well as the conservation of energy, present 

 insuperable difficulties to the vitalist. Heat and muscular work, 

 ciliary and amxboid movements, not least electricity, cannot be 

 generatett in animals otherwise than by conversion of potential 

 into kinetic energy, by oxidation of carbon and hydrogen. For 

 this nutritive matters— air, warmth, moisture, and for plants 

 light (the " integrating stimuli" of J. Miiller) are indispensable 



* " Ucber Neo-Vitalismus." Von du Bois-Reymond. Silzungs Uericbtc der 

 Akademie dcr Wissei)scli:iften zn Ljcrlin. Oefiuiulicfie Sitzuug^iir Fcicrdcs 

 Lcibnizischen Jahrcslagcs voiii 38 Juni, 1894. 



