March 15, 1894] 



NA TURE 



455 



that these are really distinct, for both can be accounted 

 for by changes in the magnetic field in which the con- 

 ductor is situated. The field in one case is produced 

 by magnets, in the other case by current-carrying con- 

 ductors. Ic would have been well to point out this 

 connection between the two things; in fact, the idea of a 

 conductor carrying a current as equivalent to a certain 

 magnetic distribution is in many cases very helpful 

 in enabling the nature of the magnetic fields of con- 

 ductors to be estimated, and the conductors to be properly 

 arranged for the purpose in hand. 



We took exception before to ihe statement in p. 12 

 that "the energy W of a current in a coil at any moment 

 is expressed by the product of the current (C) and the \ 

 electromotive force (E) that is W--EC," and we are 

 sorry it has escaped revision. Of course the authors 

 are perfectly aware that EC is in reality power or activity, 

 not energy, and merely use a very common but inaccu- 

 rate mode of speaking of the quantity EC. The energy j 

 of the current C in a coil is i LC^, where L is the self- 

 inductance of the coil, and the expression ought to be 

 reserved for this quantity. 



Experienced electricians like the authors may and do 

 avoid error from the adoption of popular but inaccurate 

 language ; but the mental confusion of power with energy 

 is very common, and has led to the most absurd con- 

 clusions as to the electrical efficiency in the circuits of 

 generators and motors. The misinterpretation, which 

 used to be so common, of the so-called law of Jacobi is 

 a case in point. In their anxiety for brevity of statement 

 and intelligibility to practical men, the authors, it seems 

 to us, run some risk of being seriously misunderstood. 



The chapter on the theory of the Bell telephone is 

 lucid, and gives a very good account of the various 

 theories that have been advanced from time to time re- 

 garding molecular action, &c. Mr. Heaviside's simple 

 explanation (given also, if we mistake not, by Mr. 

 Trouton) of the part played by the permanent magnet in 

 the telephone is stated at p. 28. 



Chapter xxxi., on the limiting distance of speech, con- 

 tains a clearly expressed summary, of course without 

 any attempt at quantitative discussion, of the con- 

 ditions of working an ordinary submarine or under- 

 ground cable, of which the true theory, and therefore 

 also, it may be rem irked, the practice, was given 

 long ago by Lord Kelvin. Mr. Preece has had an 

 immense amount of practical telephonic experience ; 

 but we are not convinced that in circuits composed of 

 non-magnetic metals, with rapid alternations of the 

 kind concerned in speech-telephony, the influence of 

 electromagnetic inertia is so slight as the authors seem 

 to regard it. 



We heartily commend this work to the technical 

 readers to whom it is addressed. The account of 

 telephone practice which it contains is worthy of all 

 praise, and it will prove not only a most useful work of 

 reference, but from its size a readily carried about and 

 consulted handbook for all engaged in such work. We 

 wish it all success, and a speedy reissue in a new edition, 

 when the few improvements we have suggested may 

 easily be made. 



A. Gray. 

 NO. 1272, VOL. 49] 



G UN THERS BA CTERIOLOG V. 



Einfuhru7ig in das Studium der Bakteriologie mit beson- 

 derer Beriicksichtigung des mikroskopischeji Technik. 

 Fiir Aerzte und Studireitde. By Dr. Carl Giinlher. 

 Third edition, 1893. 376pp. (Leipzig: Georg Thieme.) 



ACTIVITY in the bacteriological world shows no 

 signs of decreasing, and v.'hilst text-book after 

 text-book make their appearance, new editions of older 

 works follow one another in rapid succession. 



The first edition of Dr Giinther's book was published 

 in 1890, and now we have already before us the third 

 edition. A review of the second edition having appeared 

 in these columns in March, 1893, it will only be necessary 

 to draw attention briefly to some of the principal 

 additions and alterations in the present volume. 



The fact that 100 pages of new material have been 

 added, is in itself a guarantee that the author has not 

 failed to incorporate a great deal of fresh work, and, 

 indeed, on going carefully through the letter-press, the 

 reader is struck by the extreme care and thoroughness 

 with which the revision has been carried out. 



The section introductory to the special description of 

 pathogenic bacteria has been increased from nineteen to 

 thirty-one pages, and now contains a comprehensive re- 

 view of the recent work on the subject of immunity. 

 There is, however, no mention of the experiments in this 

 direction which have been made with the glanders bacillus 

 by Kresling, Semmer, and Wladimirow and Semmer, and 

 which appeared early last year in the Russian journal. 

 Archives des Sciences Biologiques, issued by the Imperial 

 Institute of Preventive Medicine in St. Petersburg. In 

 the account of the tubercle bacillus we find five additional 

 pages, and a more moderate view taken of the value of 

 tuberculine as a cure for consumption than appeared in 

 the previous edition. 



But, as was to be expected, it is in the description of 

 the cholera comma bacillus that the largest amount of 

 fresh material has been incorporated, close upon twenty 

 extra pages having been found requisite to bring the 

 work up to date. The various methods for the correct 

 diagnosis of the cholera organism are very fully given, 

 as well as the numerous devices for its isolation from 

 water when present with other bacteria. Amongst the 

 more important comma-shaped organisms endowed with 

 pathogenic properties is included the vibrio beroliiiensis, 

 which was found last summer by Neisser in the Berlin 

 water supply. The account given of this vibrio is 

 necessarily very slight, for Neisser's paper had not yet 

 been published in full. This organism resembles the 

 cholera comma bacillus very closely, and appears to be 

 distinguished from the latter only in the appearance of 

 the colonies on gelatine plates ; but these differences 

 are so slight, depending chiefly on the finer granulation 

 of the contents and the less irregular contour of the 

 colonies, that it is difficult not to regard it as a variety 

 of the cholera vibrio. 



Amongst the twenty-four saprophytic bacteria men- 

 tioned, the nitrifying organisms are conspicuous by their 

 absence. The investigations made both in this country 

 and on the continent have now firmly established the 

 existence and individuality of these organisms, and it is 



