66 



NATURE 



[September 18,1919 



electric fields to a much, greater extent than enhanced 

 lines of the same element. 



Although there is a general belief that underfed 

 individuals are more susceptible to infection than well- 

 fed persons, and that when the former contract a 

 disease they show less resistance and are more prone 

 to succumb to it, there is no definite scientific evidence 

 even of a general character to support the theory. 

 The study of the interesting question whether the 

 immunity of an animal to disease is affected by a 

 rigorous and prolonged dietetic deficiencv is a natural 

 outcome of the work on accessory food 'factors which 

 has recently been carried out at 'the Lister Institute, 

 and the current issue of the Biochemical Journal con- 

 tains a suggestive paper on the subject by Dr. S. S. 

 Zilva. Immunity is a complicated biological pheno- 

 menon which does not lend itself to quantitative 

 estimation, but certain phenomena which accompany 

 it, such as phagocytosis, complement fi.\ation, and 

 agglutination, can be estimated quantitatively for com- 

 parative purposes. Dr. Zilva has studied the effect on 

 amboceptor and agglutinin formation and the comple- 

 ment content of the blood of rats, of diets deficient in 

 (a) the elements calcium, iron, potassium, chlorine, 

 phosphorus, and sodium ; (b) certain amino-acids ; and 

 (c) the antiscorbutic, antineuritic, and fat soluble A 

 accessory factors, the rat be-ing the animal employed. 

 The diets investigated were (i) those low in ' the 

 dements mentioned; (2) those containing 12 per cent. 

 and 8 per cent, of caseinogen as a source of protein; 

 (3) those containing 18 per cent, of gliadin as the 

 sole source of protein ; and (4) those deficient in each 

 of the three accessory food factors. As a result of 

 several of the deficiencies the animals exhibited 

 restricted growth and poor condition, but, except when 

 the diet was deficient in phosphorus, no differentiation 

 in the titres of the agglutinins and ambocentor could 

 be recorded. Guinea-pigs, whether fed on an un- 

 restricted mixed diet, quantitatively restricted mixed 

 diet, or a scorbutic diet', showed no difference in the 

 amboceptor and agglutinin titres or in the complement 

 activity of their blood. 



The useful select list of scientific and technical 

 books published in the Descriptive Catalogue of the 

 British Scientific Products Exhibition, 19 19, has, with 

 the permission of the British Science Guild, been 

 issued separately in pamphlet form bv Messrs. A. and 

 F. Denny, 147 Strand, London, W.C.2. The list 

 gives in sixty pages the bibliographic particulars of 

 standard books in the English language in sixteen 

 branches of applied science, from aeronautics to wire- 

 less telegraphy. The date and price of the existing 

 edition are shown in each case, and every volume in 

 the list is on sale, so that any of the bo'oks ordered 

 can be obtained without difficulty. Messrs. Denny 

 will be glad to send a copy of the list to anyone 

 who will apply to them for it. 



The following volumes are in active preparation 

 for publication by the Hakluyt Society :—" The 

 Chronicles of Muntaner," translated and edited by 

 Lady Goodenough ; "Jons Olafssonar Indiafara," 

 translated by Miss B. Phillpotts, edited by Sir R. C. 

 Temple, Bart., 2 vols.; "William Lockerby's Tournai 

 in Fiji, 1808," edited by Sir E. F. im Thu'rn and 

 L. C. Wharton; "A Description of the Coasts of 

 East Africa and Malabar in the Beginning of the 

 Sixteenth Century," by D. Barbosa, translated by 

 L. Dames, vol. ii. ; and "Anales del Peru," bv L. F. 

 Montesinos, translated and edited by P. A. .Means. 



A lengthy and interesting catalogue (No. 181) has 

 just been circulated bv Messrs. W. Heffer and Sons, 

 Ltd., Cambridge. The books (more than 1600 in 

 NO. 2603, VOL. 104] 



number) are of a miscellaneous character, but there 

 are sections devoted to archseologv, folk-lore 

 anthropology, and kindred subjects; Irish literature, 

 folk-lore, and archaeology; and science and mathe- 

 matics. In addition, Messrs. Heffer direct attention 

 to collections of flint and bronze implements and of 

 pottery which they have for disposal. 



Messrs. George Bell and Sons, Ltd., have completed 

 arrangements with Prof. Moureu for the publication 

 of a translation of " Notions fondamentales de chimie 

 organique." The translation is being made of the 

 fifth French edition, in which additional space is 

 devoto'd to a more extensive treatment of stereo, 

 chemistry, and of the relations between chemical con- 

 stitution and physical properties. There will also be 

 an additional chapter on dyestuffs. 



OUR ASTRONOMICAL COLUMN. 

 Comets.— Miss Vinter Hansen and Mr. Fischer 

 Petersen have deduced elliptical elements for the 

 comet 1919b (Brorsen-Metcalf), and give the following 

 ephemeris : — 



For Greenwich Midnight. 



Sept. 19 

 21 

 23 

 25 

 27 

 29 



R.A. 



h. m. s. 



12 7 43 

 12 1 24 

 n 56 36 



II 52 52 

 II 50 o 



u 47 SO 



N. Dec). 



42 46 

 3854 



35 30 

 32 28 



29 43 

 27 II 



Log r 

 98967 



98577 

 98168 



Log A 



9-5175 



9-5935 

 9-6647 



Prof. Wolf noted that at the end of .August the 

 comet was easily visible to the naked eye as a large, 

 round nebula, with central condensation, and a tail. 

 The theoretical brightness is now diminishing, but 

 there is likely to be an increase in physical brightness 

 as perihelion is approached (about October 17). The 

 comet is in conjunction with the sun on September 22 ; 

 after that date it may be observed to most advantage 

 in the morning sky. 



.M. Ebell gives the following continuation of the 

 ephemeris of Kopff's periodic comet 1919a : — 



For Greenivich Midnight. 



Sept. 



On_ September 24, log r = o-2755, logA = oo74o, 

 magnitude 117. 



Continuation of the ephemeris of comet 1919^ : — 



For Greenwich Midnight. 



R.A. N. Decl. , R.A. 



. h. m, s. u , h. m. s. 



Sept. 18 1449 5 16 o Sept. 30 15 12 47 



22 145646 14 16 Oct. 4 15 21 8 



26 15 4 40 12 3c 8 15 29 42 



N. Decl. 



o , 



lb 44 



857 



7 ID 



The comet is brightening slowly, its magnitude on 

 October 8 being 8-5. 



The Blink MicRoscopE.^Mr. R. T. .\. Innes has 

 an article on this subject in Scientia for September. He 

 is one of the chief workers with this instrument, so 

 he speaks with authority. It is unrivalled as the 

 readiest means of picking out all the large proper 

 motions on a pair of plates. Taking the smallest 

 proper motion that can be detected in the case of 

 plates taken twenty-five years apart as ij" in this 

 interval, or 5' per century, Mr. Innes states that 

 there are about three such stars in each square 



