164. 



NATURE 



[August 3, 191 1 



mittee (Calcutta) he conducted a series oi experiments 

 upon the drug, collected under different conditions and at 

 different seasons. He finds that the resin obtained from 

 the rhizome collected after flowering is much richer in 

 podophyllotoxin than the sample he examined some years 

 ago, and that it contains about twice as much ppdophyllo- 

 the resin of P. peltatutn. 



A papi r "a the composition of diabetic foods, by Mr. 

 F. W. F. Arnaud, gave rise to a vigorous discussion. 

 The author gave the results of the analysis of twelve 

 different samples of gluten bread and flours, the products 

 of seven manufacturers, which showed that the products 

 of one manufacturer alone were satisfactory. Nine of the 

 products contained from 40 per cent, to 70 per cent, of 

 starch. The author cannot confirm the statement, fre- 

 quently made in advertisements, that the starch has been 

 altered, either by the qualitative iodine test or the micro- 

 scope. A sample of an expensive diabetic food was found 

 to consist of ordinary flour which had merely been heated, 

 fn the course of the discussion it was suggested that the 

 conference should take some action with a view to the 

 repression of the sale of ordinary bread and flour as 

 specially prepared diabetic foodstuffs, and it was finally 

 decided to refer the paper to the executive with the object 

 of considering whether the attention of the British Medical 

 Association should be directed to the facts disclosed. 



fn a paper on white precipitate, Mr. G. D. Elsdon 

 described a method for the estimation of mercury. He 

 confirms the statement made on previous occasions that 

 tin' sulphide method gives results that are sometimes too 

 high, but contends that the process is. in respect to its 

 accuracy, no worse than the others in general use, and is 

 to be preferred on account of its speed and simplicity. He 

 also described a method of analysing white precipitate oint- 

 ment for the purposes of the Sale of Food and Drugs Acts. 



Mr. H. Finnemore communicated a briei note on solu- 

 tion of sodium ethyiate. This liquid becomes brown on 

 keeping, the change in colour being due to the action of 

 the alkali on the acetaldehyde present in absolute alcohol. 

 The use of methyl alcohol in place of ethyl alcohol is 

 suggested; a sample of solution of sodium methylati 

 showed no trace "I discoloration after two years. 



Other papers read in the science section included a note 

 on the constitution of commercial bismuth subchloride, b\ 

 Mr. J. B. P. Harrison ; notes on arsenates of strychnine 

 and strychnine hypophosphite, by Mr. D. B. Dott ; and 

 a paper on the moisture and ash contents of medic ina! 

 extracts, by Messrs. K. C. Allen and T. Brewis. 



In the Practice Section a paper on the education of the 

 pharmai ist was read by Dr. F. Beddow. He expressed 

 iIt opinion that the present system of educating the 

 pharmacist i- nol an ideal one from the teacher's point of 

 view, sine,- a large majority of students do little or nothing 

 until they are old enough to sit for their final examina- 

 tion : thev try in compress all their work into a few 

 months, the result being a process of cramming. So far 

 as possible, educationists would like to minimise the 

 importance of the examination and increase the import- 

 I Hi' education : and in Dr. Beddow's view the 

 proposed pharmaceutical curriculum (Nature, February 2;,, 

 p. 564) is a step in this direction, for it substitutes to some 

 extent proof of education for examination. 



A paper was also r.ad by Mr. !•'.. F. Harrison on secret 

 and proprietary remedies, and af thi close >ct the discussion 

 1 resolution was passed calling upon the Government to 

 institute an inquiry into the sale of these products. The 

 position of pharmacists under tin proposed national 

 insurance scheme was also discussed. 



Sir Edward Evans was elected president for the en uing 

 year, and an invitation 10 hold the next meeting o) the 

 conference at Edinburgh was accepted 



THE SCENTS OF BUTTERFLIES. 1 



\ MONT, all the country sights of spring, summer, and 

 early autumn, I suppose there is none more familiar 

 than that of the common while butterflies. Thev an- to bi 

 een, as we know, everywhere; haunting woods, hedgerows, 

 lanes and gardens, crossing heaths and meadows, and 

 visiting at time's not only parks and squares, but even 



1 Discourse delivered :it the Royal Institution on Friday, March 3, by Dr. 

 F. A. Dixey, F.R.S. 



NO. 2 179. v O L - 87] 



streets in the heart of London. Of these insects then an 

 in this country, as is no doubt known to many of you, 

 three especially abundant kinds. One of these is the large 

 white; the other two species are smaller. These 

 two latter kinds are much alike when seen on the wing ; 

 but on a closer view they are easily distinguished, the 

 most obvious mark of difference being the presence in one 

 of them of greyish-green streaks, following the course of 

 the so-called " veins " or " nervures," on the under surface 

 of the hind wing. From this character the form in question 

 gets its common name of the "green-veined white." If 

 anyone will capture a male green-veined white (easily 

 distinguished from the female by the much slighter spotting 

 of the male's upper surface), and will brush the upper 

 surface of the fore or hind wing with a camel-hair pencil, 

 he will become conscious of a strong agreeable odour like 

 that of the so-called " lemon-plant." On further examina- 

 tion he will find that this perfume emanates from the 

 wings of the butterfly, and is strongly perceptible on the 

 brush with which the wings were rubbed. The rubbing 

 process has, of course, dislodged large quantities of the 

 minute scales with which the wings of this insect. like 

 those of butterflies and moths in general, are clothed ; and 

 these dust-like scales, adhering to the brush, have in some 

 way or other carried with them the characteristic odour of 

 the butterfly. A similar scraping or rubbing of scales from 

 the under surface of the wings does not emit the odour, nor 

 is it found in association with any scales from either 

 surface of the female. 



We find, then, that in this butterfly the perfume attaches 

 to the scales in one- particular situation, namely, the upper 

 surface of the wings of the male insect. This fait 

 obviously suggests that we should examine these particular 

 scales in order to find out whether they present any 

 differences from the scales which appear to be odourless. 

 On applying the microscope to the scraping which carries 

 the scent, we find at once an answer to our question. The 

 great majority of the scales are of the ordinary well-known 

 kind, consisting of an elongated flattened lamina, provided 

 at one end with a short quill-like footstalk by which they 

 are attached to the membrane of the wing, and frequently 

 showing at the other extremity ■"' more or less marked 

 indentation. But among these will be found certain scales 

 of an entirely different appearance. These latter scales in 

 the insect before- us an- somi'wli.'it bean-shaped, carrying a 

 long footstalk which ends in an almost circular disc, anel 

 tapering at the other extremity to a point. But the greatest 

 peculiarity of these special scales is to be found in the 

 plume-like- structure which crowns -heir apical portion. 

 Under a low power of the microscope the appearance is 

 that of a tuft of line transparent hairs, strongly suggestive 

 of the vibratile cilia which are so familiar in animal and 

 vegetable histologj ; but these hair-like- processes, unlike the 

 cilia, have nee fee uhy of active movement, and under a 

 high power they bear rather the aspect of minute tubes, in 

 many ras,-s seeming be be open at their free extremity. 

 On examining a similar scraping from the under surface 

 eel the mail-, or from either surface of the female wing, we 

 find only scales of the ordinary kind; the special "plume- 

 scales," as they have been called, being invariably absent. 

 Inasmuch, then, as tin- characteristic fragrance is found 

 only in scrapings which contain the plume-scales, we an 

 justified in concluding that these remarkable structures act 

 as carriers of the perfume. 



So far we have considered only one species of butterfly, 

 the common green-veined white-; but thi question will 

 naturally be asked -what about other butterflies, the other 

 common while's, for example? Is this flowery perfume a 

 peculiarity of one species only, or is the property of 

 emitting a fragrant odour shared by other related in ■ 

 In order to answer this question, lei us suppose that we 

 make a series i trials on the second species of smaller 

 common while-, the- small cabbage or garden white, as it is 

 usually called. Here, again, no trace of a flowery odour is 

 discoverable- in the female or in scales from the lower 

 surface of the- wings in the- male; but, as before, the upper- 

 surface of the- wines in the latter sex will be fecund to be 

 scented, and, also as before, the scent will be found to 

 adhere to the scales removed by scraping or brushing from 

 the upper surface. Examining the scented scraping micro- 

 scopically, we find that her.-, too. are a number of plume- 

 scales mixed in with scales of the ordinary type-. Th'-se 



