July 26. 1900] 



NA TURE 



291 



to the eighteenth day after section, the organ can be 

 excited to discharge, but the shocks are weaker than 

 normal. After the nineteenth day, however, no response 

 is obtained to stimulation either of the nerve or of the 

 electrical organ itself. Thus the irritability of the organ 

 disappears with that of the nerve, whereas a muscle is 

 excitable long after the degeneration of its motor nerve 

 with end-plates is complete. It may be mentioned that 

 the organ-current, or current of rest, and the irreciprocal 

 conductivity diminish during the period of lowered irrit- 

 ability of the organ, and are absolutely abolished after 

 the nineteenth day, thus pointing to the excitatory nature 

 of both these sets of phenomena. 



The experiments on the action of curare are less satis- 

 factory, owing to the enormous doses (i grm. for a fish of 

 1200 grms.) which are necessary to paralyse the indirect 

 excitability of the electrical organs. Since in these large 

 doses the curare excites central discharges, it is necessary 

 to cut all the electrical nerves to prevent paralysis by 

 fatigue. In this case, however, with a sufficient dose of 

 curare, direct and indirect excitability are abolished simul- 

 taneously. The same interdependence of direct and in- 

 direct excitability is observed in paralysis by fatigue, in 

 marked contrast to the behaviour of voluntary muscle, 

 where a muscle on direct stimulation gives a practically 

 normal contraction after complete fatigue by stimulation 

 of its nerve. 



Veratrin, which causes a marked prolongation of the 

 excitatory change in skeletal muscle, was found by 

 Garten to produce a somewhat similar effect on the 

 electrical discharge of the torpedo. This drug, however, 

 diminishes and very rapidly abolishes the direct and in- 

 direct excitability of the electrical organ, and no proof is 

 . afforded that the prolonged response may not be due to the 

 state of artificial " fatigue " produced by the drug, or that 

 it is in any way specific. Waller's experiments have 

 shown that veratrin has practically no action on the 

 nerve, and although Garten quotes certain of his own ex- 

 periments which appear to indicate an action of this drug 

 on non-medullated nerve, the strength of the solution em- 

 ployed must be regarded as too great for the demon- 

 stration of the specific action of the drug. 



We cannot, therefore, regard the experiments with 

 veratrin as detracting in any way from the support 

 afforded to the nerve-ending theory of excitation by the 

 results of nerve-section. It is remarkable that a change 

 which, as the current of action in nerve, needs all the ap- 

 pliances of a well-fitted laboratory for its demonstration, 

 should, by a mere subdivision of the fibrils and their 

 enclosure in compartments separated by non-excitable 

 partitions, be able to produce the strong shocks of high 

 intensity which characterise the discharge of the whole 

 organ. No better demonstration could be afforded of the 

 futility of those hypotheses which would explain the 

 passage of the nerve-impulse as a mere propagated 

 polarisation, and would deny any energy-producing 

 changes in the axis-cylinder itself. The absence of 

 fatigue in medullated nerve does not imply absence of 

 chemical change, but merely equivalence of disintegration 

 and reintegration, an equivalence probably connected, 

 as Waller has suggested, with the presence of a 

 medullary sheath. E. H. S. 



NO. 1604, VOL. 62] 



FLUORINE. 

 Le Fluor et ses Composds. Par M. Henri Moissan, Pp. 

 xii -I- 396. (Paris: G. Steinheil, 1900). 



THERE could scarcely be a greater contrast than 

 that between the gaseous substances most recently 

 added to our list of elements ; fluorine on the dne hand, 

 argon and its companions on the other. The existence 

 of the hypothetical element fluorine was postulated in 

 many well investigated compounds as early as the begin- 

 ning of the present century ; yet, on account of its intense 

 chemical activity^ fluorine was not prepared as a free 

 element until 1886, despite the numberless attempts 

 which had been made to isolate it in the intervening 

 period. Argon, on the otlier hand, owing to its absolute 

 inertness, and to the fact of its occurrence along with the 

 very inert nitrogen, led an unsuspected existence until 

 1894, although it was contained in enormous quantities in 

 the atmosphere — a constant subject of investigation. The 

 compounds of fluorine, then, were known long before 

 the element itself, — compounds of argpn are still 

 wanting. Indeed, as has been pointed out (Sedgwick, 

 "Argon and Newton," p. 2), the name element in the 

 ordinary sense cannot properly be applied to argon and 

 its companions at all, since that term implies the exist- 

 ence, or at least the possibility of existence, of com- 

 pounds concerning which we are still in total ignorance. 

 As yet there is no chemistry of argon. 



The time, however, has now arrived when fluorine and 

 its compounds can be brought under review so as to give 

 a picture of the element in itself and in its combinations, 

 which in main outlines, at least, may be looked upon as 

 final. Prof Moissan was obviously the man to execute 

 this task ; he has fortunately undertaken it, and the book 

 before us gives the result of his labours. As evidence of 

 the extent of the author's research, we may adduce the 

 bibliography given as appendix, which occupies eighty- 

 five pages, and contains references to about six hundred, 

 books and papers. These references are arranged alpha- 

 betically according to authors, and also chronologically, 

 beginning with Agricola, 1558, and ending with the year 

 1899. 



In the book itself the author's investigations have 

 naturally the first place, and one of the chief points of 

 interest is that M. Moissan not only gives us an account 

 of his apparatus, experiments and results, but also of the 

 leading thoughts which guided him from one experiment 

 to another, until the culmination was reached in the 

 liberation of the gaseous element. The student begin- 

 ning research could not find a more stimulating record of 

 failure and eventual success than that afforded in Chapter 

 i., on the isolation of fluorine. Chapter ii. deals with the 

 most recent apparatus for the production of fluorine by 

 electrolysis. At a temperature of about - 80^, attained 

 by the evaporation of a mixture of solid carbonic acid 

 and acetone, it is possible to use an electrolytic vessel 

 of copper instead of platinum, provided that the hydro- 

 fluoric acid employed is free from water. This substi- 

 tution brings elementary fluorine within the scope of any 

 well-equipped chemical laboratory. Chapter iii. deals 

 with the physical properties of fluorine, its liquefaction, 

 and the action of the liquid on various substances. In 



I 



