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NATURE 



[April 



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encountered amongst pathogenic bacteria. The 

 word "transmutation " is employed by the author 

 to indicate the transformation of members of one 

 recognised species into those of another, and he 

 refers in detail to the arbitrary methods hitherto 

 employed by bacteriologists for the differentiation 

 of bacterial species. Apart from two or three 

 pages in which the author's own experimental 

 work is briefly described, the book is mainly a 

 study of bacteriological literature in the English 

 language. A large part of the abundant publica- 

 tions in foreign languages is either not dealt with 

 at all, or is analysed frorn English abstracts. There 

 is a good deal of reiteration, certain observa- 

 tions, often obsolete, being utilised again and 

 again in different parts of the book. The use of 

 the apostrophe in "Aertryck's bacillus" seems to 

 indicate that the name is that of a man instead 

 of that of a place. The last chapter, entitled 

 "The Enzyme Theory of Disease," deals with the 

 idea that most of the attributes of pathogenic 

 bacteria can be referred to the activities of ultra- 

 microscopic bodies of the nature of enzymes, and 

 the author considers that this may be the means 

 by which bacteria may exchange many of their 

 characters and functions without themselves under- 

 going transformation. . 



The Examination of Materials hy X-rays. A 

 General Discussion held by the Faraday Society 

 and the Rontgen Society, Tuesday, April 29, 

 1919. Pp. 88 + 64. (Reprinted from the 

 Transactions of the Faraday Society, vol. xv., 

 part 2, 1919.) (London : Faraday Society, 

 1919.) Price 135. 6d. 



The Faraday and Rontgen Societies did good 

 work when they held a joint meeting in April last 

 year and thrashed out the position as regards the 

 achievements, possibilities, and limitations of the 

 method of the examination of materials by X-rays. 

 The present volume will form a most useful 

 jumping-off point for the investigator or manu- 

 facturer who desires to know what had been 

 achieved in industrial radiology up to 1919. The 

 contributors to this "symposium number " include 

 many of the leading radiographers in this country 

 who have not confined their interests to medical 

 radiology. Not all the noteworthy work achieved 

 during and since the war was, however, available 

 for publication when the discussion was held. 



The first paper, by Prof. W. H. Bragg, forms a 

 delightful introduction to the subsequent papers 

 and discussions, which deal with such varied 

 subjects as steel, light alloys, aircraft timber, 

 carbon electrodes, X-ray plates, etc. There are 

 many excellent reproductions of radiographs. 



One realises, from a close reading of the 

 volume, that we stand only on the threshold of 

 radiology, and big and unexpected developments 

 are probable during the next ten years. Both the 

 Rontgen and Faraday Societies are to be con- 

 gratulated on the results of the meeting. We 

 understand the volume is procurable from the 

 secretary of either society. 



NO. 2631, VOL. 105] 



Commercial Oils : Vegetable and Animal. With 

 Special Reference to Oriental Oils. By I. F, 

 Laucks. Pp. viii+138. (New York: John 

 Wiley and Sons, Inc. ; London : Chapman and 

 Hall, Ltd., 1919.) Price 65. net. 

 This is a handy little book, intended, not for the 

 oil chemist, but for those persons concerned in the 

 oil industry who have no knowledge of chemistry, 

 or at least no knowledge of it as applied to oils. 

 There are no doubt many such who will often 

 desire to understand what is meant by the variou:: 

 analytical tests and terms used in the specifica- 

 tions on which large users of oil base their con- 

 tracts of purchase. For example, on p. 70 of the 

 book there is a specification for oil to be employed 

 as a lubricant for aircraft engines ; this stipulates 

 that the oil must have (inter alia) a certain iodine 

 number, saponification value, flash point, and so 

 on. The author describes in simple terms what 

 these and similar phrases mean, and how they 

 are employed as criteria of the purity and quality 

 of the oil. He gives also short descriptions of 

 the principal oils and fats met with in commerce, 

 and has some very useful advice to offer on 

 methods of taking samples. Even the expert may 

 peruse this part of the volume with advantage, 

 and the non-technical reader should at least have 

 an intelligent idea of the whole subject after study- 

 ing Mr. Laucks 's book. 



The Birds of the British Isles and their Eggs. By 

 T. A. Coward. First series. Comprising 

 Families Corvidae to Sulidae. Pp. vii + 376+159 

 plates. (London and New York : Frederick 

 Warne and Co., Ltd., 1919.) Price 125. 6d. 

 net. 

 This volume of "The Wayside and Woodland 

 Series " of handy pocket-guides affords a popular 

 account of our British birds. Such a work, espe- 

 cially if embellished with good coloured plates of 

 the various species and their eggs, and accom- 

 panied by trustworthy letterpress, has long been a 

 desideratum. The figures of the birds are repro- 

 ductions, much reduced in size, of those in the late 

 Lord Lilford's much-prized book. They are 159 

 in number, and most of them are decidedly good ; 

 but others are disappointing from the fact that 

 the three-colour process has not been equal to 

 doing them justice. The figures of the eggs, which 

 are from one of the editions of Hewitson's well- 

 known book, are disappointing for the same 

 reason, and will mislead the tyro who attempts 

 by their aid to name many of his specimens. There 

 is also an acceptable series of black-and-white 

 illustrations devoted to nests, etc. 



Mr. Coward's letterpress, as one would expect, 

 is good, but it is questionable if his excellent 

 descriptions of habits have not been awarded too 

 much space at the expense of other sections, 

 among them the British distribution of the more 

 or less local species. Given a knowledge of the 

 bird and where it is likely to be found, its various 

 activities may be observed by those who care to 

 devote their attention to the delights of bird- 

 watching. This neat and useful little volume- — the 

 first of the series on birds — will, no doubt, be 



