64 



NATURE 



[March 28, 19 18 



firing," compiled in "drill book" style, but illus- 

 trated with most excellent diagrams, which are 

 almost self-explanatory, is a section on grenade 

 tactics. A description of French and German 

 ^rrenades follows, and then a section on explosives 

 used in grenades. Here the author might well 

 have been more explicit; in an attempt to be 

 concise much of the information has been too con- 

 densed to be clear, We read, for example : " Picric 

 acid. A yellow crystalline prepared "from coal tar. 

 A by-product of gas manufacture." Again: 

 " Lyddite or picric acid. Consists of melted and 

 solidified picric acid. Vaseline is used to melt it." 

 The alternative for benzol is given as benzine. 

 Under cordite no reference is made to M.D., but 

 only to the old Mark I., and the nitroglycerine 

 content of this is wrongly stated. The acetone 

 used for incorporation is described as merely 

 "acetone to harden." 



The practical part of the book will no doubt be 

 of assistance to students of grenade work ; it is 

 essentially a soldier's book, but its value would 

 have been greater had the author not attempted 

 to impart information in too few words. 



Therapeutic Immunisation : Theory and Practice. 



By Dr. W. M. Crofton. Pp. 224. (London : 



J. and A. Churchill, 1918.) Price 75. 6d. net. 

 Ix the earlier chapters of this book the author 

 surveys the processes underlying immunity, and 

 describes the preparation and properties of toxins 

 and antitoxins and the agglutination and precipitin 

 reactions. The principles of therapeutic immun- 

 isation by means of vaccines are then considered, 

 and finally the practical applications of therapeutic 

 immunisation to diseases of the alimentary canal, 

 the respiratory system, and other regions of the 

 body are described. The author's system does not 

 appear to differ essentially from the customary 

 routine, with the exception that in some instances 

 he advocates the continuance of treatment until 

 very large, doses of vaccine are reached, e.g. 

 30,000 million cocci in the case of some staphylo- 

 coccic infections. The use of various iodine pre- 

 parations is also recommended as an adjunct to 

 vaccine treatment in some infections. For the 

 treatment of tuberculosis, tuberculins made by 

 extraction with benzoyl chloride, which is a sol- 

 vent for the waxy constituent of the tubercle 

 bacillus, are considered to be superior to the 

 ordinary tuberculins. 



In addition to vaccine treatment, the use of 

 vaccines for prevention is also considered where 

 they are applicable, as in the cases of typhoid 

 fever, cholera, plague, etc. 



The book gives a useful summary of the prac- 

 tice of vaccine treatment. The practical details of 

 the isolation of the micro-organisms concerned and 

 the preparation of the vaccines therefrom are, 

 however, scarcely touched upon. Full directions 

 are given for the dosage of vaccines and for the 

 proper spacing of the doses, and these will be 

 found very useful by the practitioner who is adopt- 

 ing vaccine treatment. R. T. H. 

 NO. 2526, VOL. lOl] 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous cotmnunications.] 



The Stimulation of Plant-growth by Electric Fields. 



In his letter on the sbove subject in Nature of 

 March 7 "J. L." states that "the procedure suggests 

 that it is the field of force that is expected to produce 

 the stimulation. The comparatively trifling amount of 

 electricity that leaks from the wires into the atmo- 

 sphere could scarcely produce directly any sensible 

 effect." It is perfectly clear, however, that Lemstromi 

 —the professor of physics at Helsingfors who started 

 about thirty years ago the modern phase of electro- 

 culture with overhead wires— held the view that the 

 current leaking from the wires and passing through 

 the plant was responsible for the effects on plant 

 growth which he describes. For the purpose of in- 

 creasing the discharge he used fine wires, o-6 mm. in 

 diameter, placed only 40 cm. above the plants, 

 and provided with "barbs" 2 cm. long. In 

 similar experiments in this country the fine wires have 

 been retained, though the "barbs" are usually dis- 

 pensed with. 



It is true that our knowledge of the effects of 

 electricity on plant growth is practically nil, 

 and that the currents in question are very small, being 

 of the order of i mllliamp. per acre in some recent 

 experiments with wires about 7 ft. high. It is, how- 

 ever, not implausible to assume, although, of course, 

 there are other possibilities, that the passage through 

 the plant of such minute currents may alter the rate of 

 some of its metabolic processes, and so affect plant 

 growth. 



In the experiment suggested by "J. L.," where the 

 overhead wire Is supposed to be protected from leakage, 

 as, for example, by encasing it in a solid dielectric, it 

 is not clear that a discharge from the pointed aerial 

 portions of the plant would continue unaltered. 

 Although a strong wind may prevent a large part of 

 this discharge from passing to the dielectric enclosing 

 the wire, such a wind will scarcely be able to prevent 

 other atmospheric ions from being attracted to its 

 outer surface. Air currents, in fact, will bring such 

 ions to the dielectric on which they will form a gradu- 

 allv increasing charge tending to weaken the electric 

 field' between the wire and the crop. If the overhead 

 wire be bare, but of large gauge so that leakage from 

 it is small, and its potential be increased to such a 

 value that a discharge occurs from the plants, then, 

 with a strong wind, the current passing through the 

 crop may be very much greater than that leaking from 

 the wires. ' V. H. B. 



G. W. O. H. 



Does the Indigenous Australian Fauna Belong to the 

 Tertiary? 



The statement that the indigenous mammalian fauna 

 of Australia belongs to the Mesozoic has been sC fre- 

 quently made that it has come to be generally accepted. 

 It was, therefore, not surprising to find the reviewer 

 of Cleland's "Geology," in Nature of August 2, 1917 

 (vol. xcix., p. 441), pointing out as a mistake the 

 opinion expressed in that text-4book that the fauna is 

 a Tertiary one. 



In order to ascertain the opinion of vertebrate palae- 

 ontO'logists on this point, letters were sent to Messrs. 

 J. W. Gidley, W. D. Matthew, and S. W. Williston. 



