3^4 



NA TURE 



[August i6, 1900 



The study of the glucosides may be said to date from 

 Liebig and Wohler's remarkable discovery of the decom- 

 position of amygdalin by its own ferment or enzyme 

 emulsin. The discovery of other glucosides followed in 

 fairly rapid succession. Among these may be mentioned, 

 without reference to chronological sequence : salicin, 

 derived from willow bark ; populin, from aspen leaves ; 

 iesculin, from the bark of the horse chestnut ; daphnin, 

 from Daphne mezereiim ; phloridzin, from the bark of 

 apple, pear and other fruit trees ; hesperidin, from the 

 fruit of limes, oranges and lemons ; potassium myronate 

 or sinigrin, from black mustard seed ; ruberythric acid, 

 from madder root, &c. They all undergo decomposition 

 by a process of hydrolysis into grape sugar, and at least 

 one other constituent drawn from such very varied groups 

 of compounds as phenols, alcohols, aldehydes, mainly of 

 the aromatic series, and in the case of black mustard 

 seed, from a sulphocyanide. No trustworthy explanation 

 of the constitution of these substances was, or could be, 

 forthcoming until the structure of their proximate con- 

 stituents had been ascertained. 



The most important contribution to our knowledge 

 of the glucosides in recent years has been undoubtedly 

 that of Emil Fischer in his classical researches on the 

 sugars. The formation of the glucosides of the simple 

 alcohols and phenols, and of similar compounds of the 

 mercaptans and ketones, has not only given a valuable 

 clue to the structure of the natural products, but has 

 revealed the close analogy which exists between these 

 compounds and the members of the disaccharoses (cane 

 and milk sugar and maltose). Moreover, the identification 

 of new sugars has led to the successful search for these 

 substances among the glucosides and other plant pro- 

 ducts. Rhamnose or methyl pentose is found to replace 

 glucose in several glucosides : quercitrin, hesperidin, 

 frangulin, baptisin, datiscin, &c., whilst chinovose, 

 another pentose, is contained in chinovite. 



Many other interesting points have arisen. The hydro- 

 lysing action of the enzyme accompanying one glucoside 

 has been shown, not to be confined to that glucoside, but 

 to extend to others, although, at the same time, strictly 

 limited to a particular series of compounds. The enzyme 

 of yeast has in a similar way been recognised as not 

 exclusive, although restricted in its hydrolysing power. 

 The action of emulsin and yeast on amygdalin is in- 

 structive. Emulsin effects complete hydrolysis of the 

 glucoside into benzaldehyde hydrocyanic and two mole- 

 cules of glucose, whereas the enzyme of yeast only 

 removes one glucose group. Fischer, who discovered 

 this curious difference between the two enzymes, has 

 allotted the following formula to the second product : 



QHgCH.CN 



O.CH.CHOH.CHOH.CH.CHOH.CH2OH. 



The splitting off of more than one molecule of glucose on 

 hydrolysis occurs with populin, hesperidin, helleborin and 

 others. 



All these facts are recognised and carefully recorded 

 in the volume before us. 



The work is divided into two parts. The first part 

 deals with the artificial glucosides ; the second, with the 

 NO. 1607, VOL. 62] 



natural products. In the first part, the compounds are 

 arranged in a strictly chemical order ; in the second, 

 according to the natural order of plants. In reference 

 to this arrangement, the author lays stress on the fact 

 that the study of the constituents of plants should not 

 follow a chemical classification, but should include all 

 compounds occurring in the same natural order ; because, 

 he explains, it is only in this way that the chemical, 

 morphological and anatomic properties will appear in 

 their true light. The goal of the chemist should not be 

 determined by purely utilitarian motives, but Rochleder's 

 principle should be borne in mind that " the relation- 

 ship of plants is determined by compounds of the same 

 chemical nature which they contain." 



There are one or two points mentioned in the book 

 which are new to us, and may interest our readers. It 

 appears now that sinigrin, the glucoside of black mustard 

 seed, is not hydrolysed, as usually represented in text- 

 books, without the addition of the elements of water ; 

 but the glucoside contains one molecule of water 

 CjoHigNSaKOg + HgO, and the decomposition then falls 

 into line with the hydrolysis of other glucosides, 



CioH,6NS^KOs+H.p = C3H5NCS + 0611,206 +KHSO4. 



According to Beyerinck, indigo does not occur in the 

 oldest of the indigo plants {[satis tinctorid) as the gluco- 

 side indican, as usually stated ; but in the form of indoxyl, 

 which rapidly oxidises to indigo in contact with air ; 

 whilst the glucoside indican which is found in Indigo- 

 /era lepiostachya and Polygonum tinctorium may be 

 extracted and left in contact with air without under- 

 going any change in the absence of enzymes and 

 bacteria. J. B. C. 



AN OXFORD TEXT-BOOK. 

 An Introduction to the Study of the Comparative 

 Anatomy of Animals. By G. C. Bourne, M A., F.L.S. 

 Vol. i. Pp. 258. (London : G. Bell and Sons, 1900.) 



THIS admirable little book is designed to meet the 

 requirements of the elementary examinations of 

 the leading universities of Great Britain, and though of 

 necessity largely concerned with creatures upon which 

 laboratory treatises exist in abundance, it has been so 

 framed as to supplement and not supersede certain of 

 these, the author having aimed at " the lessons that may 

 be learned and the conclusions which may be drawn" 

 rather than the detailed description of the facts them- 

 selves. The work opens with an " Introduction," in 

 which it is pointed out that in the study of natural 

 science, as in other things, something of the nature of a 

 creed is necessary for action, and there is given a 

 definition of "evolution," on the basis of the principles 

 involved in which the science of comparative anatomy 

 is said to be founded. Passing on to treat of the 

 elementary principles of morphology and physiology, the 

 author proceeds to deal with the anatomy of the frog, the 

 elements of histology of the Vertebrata, the cell and cell 

 theory, and phenomena of development up to the forma- 

 tion of the germinal blastemata. The Protozoa are next 

 dealt with, including the Mycetozoa and Volvocin^ ;. 

 and, apropos of Volvox and Zoothamnium, there follows a 

 chapter on the Protozoa and Metazoa, with a discussion 

 of their inter-relationships. The Coelenterata follow 



