444 



NATURE 



[February 7, 191: 



mode of formation of vegetable alkaloids is still 

 left open, but on the whole it is considered that 

 the work done recently rather supports the view 

 that alkaloids are formed from the decomposition 

 products of proteins. As regards the function of 

 alkaloids in plants, the view most widely accepted 

 now is that they are ultimate products of meta- 

 bolism, and pf no further use to the plant. Among 

 useful new processes of alkaloid analysis may be 

 mentioned the citrate method of estimating quinine 

 (p. 516) and thfe ferrocyanide process for quanti- 

 tativelv separating strychnine from quinine 

 (p. 518). 



The volume contains a two-hundred-page index 

 to the whole work, which is indispensable to 

 analytical laboratories dealing with organic pro- 

 ducts. The editor is to be congratulated upon 

 thfe successful completion of his lengthy task. 



C. S. 



/ 



OliR BOOKSHELF. 



Om Laegekunst hos Perserne. By A. Christen- 

 sen. Pp. 103. (Medicinsk-historiske Smaa- 

 skrlfter, 18.) (K^benhavn : Vilhelm Trydes 

 Forlag, 1917-) 

 This small work of one hundred pages constitutes 

 the eighteenth pamphlet of the Medicinsk- 

 historiske Smaaskrifter edited by Vilhelm Maar 

 and published in Denmark. We have reviewed the 

 other volumes in a previous issue, and regret that 

 an announcement in the present pamphlet indi- 

 cates that the series, for the present at any rate, 

 has reached a conclusion. The subject of Persian 

 medicine has been dealt with by many historians, 

 and Dr. Christehsen has brought our knowledge 

 up to date. He divides the matter into four 

 chapters : the Zoroaster period, ancient Islam 

 medicine, the period of Avicenna, and recent 

 Persian medicine. An appendix with a translation 

 of one of the four treatises of the " Tchahar 

 makala " of Nizami-i-Aruzi (twelfth century) com- 

 pletes the account. The medicine of the Avesta, 

 the original document of Zoroaster's religion, is 

 fully dealt with, and the influence of Ahura Mazda, 

 the all-wise spirit, in maintaining health is 

 analysed. The demoniacal concept of disease and 

 its production through the agency of Anro Maiynus 

 — the evil mind — is carefully considered. The fall 

 of the Sassanian empire in the seventh century 

 and its conquest by the Arabs has had a profound 

 influence on the subject of medicine, for it was 

 through the Arabs, notably Rhazes and Avicenna, 

 that the great works of classical antiquity were 

 restored to European learning, enriched with the 

 valuable commentaries of these diligent students 

 of the dark ages. Dr. Christensen's researches 

 constitute a distinct addition to our knowledge of 

 this interesting period. 



The " Wellcome " Photographic Exposure Record 



and Diary. Pp. 256. (London : Burroughs 



Wellcome and Co., igi8.) Price is. 



This well-known pocket-book has. all its usual 



features, in spite of the exigencies of the times. 



NO. 2519, VOL. 100] 



The main article has been rewritten, and gives 

 concise but sufficient directions for the use of 

 ' ' tabloids ' ' in all the usual photographic opera- 

 tions. It includes development by time and tem- 

 perature, tank development, factorial develop- 

 ment, fixing, intensification and reduction, and 

 printing processes, the use of various develop- 

 ment papers, carbon printing, and oil pigment 

 printing, the making of lantern slides, various 

 toning and staining processes, and colour photo- 

 graphy by means of autochrome, Dufay and 

 Paget colour plates. The mechanical calculator 

 attached to the cover, with the necessary tables 

 and lists, from which the photographer will select 

 those details that apply in his particular case, has 

 established its trustworthiness and convenience by 

 many years of experience. A useful diary, plenty 

 of space for recording exposures, a copious index, 

 sundry tables, etc., and two illustrations "from 

 the front," or very near it, complete the volume. 

 It is interesting to note that in the classified lists 

 of photographic materials there are given con- 

 siderably more than two hundred different kinds 

 of plates and films, forty-five kinds of bromide 

 paper, and twenty-nine kinds of lantern plates, 

 although German and Austrian goods are 

 excluded. 



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 communications.] 



The British Scientific instrument-making Trade. 



The progress of science as- the result of experience 

 gained during the present war will call for increased 

 effort on the part pf British manufacturers of scientific 

 instruments at the conclusion of hostilities. Moreoyer, 

 the knowledge gained by our principal enemy By virtue' 

 of the British blockade will give her a lead over us in 

 many directions, since she has been forced to bring 

 the brains of her leaders of scientific thought to bear 

 .on many problems of vital moment to the life of their 

 country. 



From this it would seem as if British scientific in- 

 strument makers were called upon to co-operate more 

 closely. than has been the case in the past, if thev are 

 to meet the competition they will be called upon to face^ 

 as soon as Germany is in a position to reconstruct 

 her industries when relieved from the burden of war.. 



The object of the present letter i« to suggest the. 

 formation of an institution which, while retaining most 

 of the features of existing scientific societies, will pro- 

 vide means for greater effort in collaboration, as re- 

 gards training, research, and propaganda, with the vie'W^ 

 of increasing the field for British-made instruments'.. 

 As was pointed out by the present writer in an article 

 in Nature of August 16, iqiy (vol. xcix., p. 488), Ger- 

 many has always realised the value of research as 

 applied to the instrument-making trade, but the same 

 cannot be said for this country. One of the first tasl<s, 

 then, confronting such an ihstitutiori, if established."' 

 would be the installation of a properly equipped and 

 staffed laboratory, in which investigations could be car- 

 ried out (i) in the interests of individual members, (2) 

 in the interests of the general body of members. It may 

 be objected that this would mean usurping the functions 



