BOOK REVIEWS 127 papers. In fact, Ruzicka (his summary essay is typically brilliant) takes note of the diversity of view- points among the writers. The book consists of eight brief pape.rs, with Stoll delivering an opening discourse on molecular structure and odor. How tortuous are the theories necessary to fit odor and structure into a pattern, and how numerous are the exceptions necessary to permit such theories to stand. Kalmus, m the second paper., deals with physiology and genetics Stiras and Demeillers write on the measurement of odor intensity Naves followed by Beets (these chapters are, to this reader, the highlights of the book) on stereochemistry and odor, and on structure and odor, respectively Wright puts forth his theory of molecular vibration, and is followed by Thompson, who refutes it and Ruzicka summarizes. That there should be clashes of opinion in a work of this sort is expected, and the Wright-Thompson debate, in that respect, is of great interest. But that there should be conflict of factual testimony is disconcerting, for it indicates that even amongst the best chemists, the reporting of work in odor continues to suffer from severe limitations. Two instances of such conflict between Stoll and Naves will be cited. Stoll: "No odorous sub- stance is known with a molecular weight above $00." Naves: "We know that organic substances with a molecular weight of 600 to 800 or more are odorous." Again, Stoll: "When isomerism is produced by an asymmetric carbon atom, i.e., as in optica! isomers, the odor of the isomers •s generally the same." Naves: "Enantiomers have dif- ferent odors and (that) the odor of the racetalc substance is different again." Two ambiguities that may lead to serious misunderstanding should be cleared up. They are from the same contributors, Stoll and Naves. The former states: "Colorists have much more difficulty in identifying a molecular structure by means of color than perfumer-chemists have when smelling an odor." If by "identifying" one means the recog- nition of a known substance, this is true if it means the elucidation of the structure of that substance, it is obviously not so. From Naves: "Whilst a substance ap- pears to be pure whatever the physical or chemical tests to which •t •s submitted, it can exhibit olfactory characteristics according to its origin." Here, the author would surely emphasize "appears to be" as the key words, admitting that there must be trace substances contributing to the odor, but not identifiable by physical and chem- ical tests. What is admirable about the work of Naves is not only the documentary evidence submitted for all assertions, but his critical evaluation of previous workers. He recognizes the difficulties that have beset odor chemists in the past because of false contentions, and with characteristic courage he names those whose work he rejects and cites reasons for such rejection. Of the stimulating debate be- tween Wright and Thompson, one is impressed, as is so often the case in olfactory theories, with the difficulties of proving one's asser- tions, and the ease with which they are disproved. Stiras and Demeillers describe an apparatus for the determination of odor intensity. The apparatus is based on a system of air dilution. Some of their reports, in this re- viewer's opinion, should have been excluded, because they are studies

128 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of mixtures of undisclosed com- position. The use of three observers and the averaging of their results, would leave much to be desired from the statistical viewpoint. Among the stimulants for thought and study, one finds a statement by Stoll that nerol and geraniol have very different odor strengths, but their thresholds of perception are rather close. Having assumed, without question or challenge, that odor strength and threshold of perception are directly proportional, this statement offers a new vista for experiment. In fact, this entire book offers a broadened field for study. The facts so difficult to verify and correlate, the viewpoints so openly divergent, the searching and the groping, are healthy symp- toms of the struggle to forge a science ofolfaction. In this struggle the achievement of Naves trans- cends his work of analysis and synthesis (elucidation of the struc- ture of the irones and their synthetic reproduction), his incredible pro- lificacy, and his co-authorship of Natural Perfume Materials the great achievement of Naves is that he has brought rigorous and disci- plined scientific methodology into a field in which its absence was frequently distressing. This is a bilingual book, part of it being in French, which is rather curious in view of the fact that most of the papers published in English were probably delivered in French, German, or perhaps Dutch. Why one paper and fragments of the discussion were not translated, while the remaining parts of the book were rendered into English, is not explained. These are lengthy but minor exceptions to a book indispensable to those interested in olfaction.-- EDWARD SAGARIN, Embassy Lab- oratories. DIE XTHERISCH•.N 0LE, Volume I, by E. Gildemeister and F. Hoffmann Akademie Verlag, GmbH., Berlin W. 8, Germany. 1956. 500 pages, 61/,. X 91/2 inches, illustrated and indexed. Price33.50D.M. Volume IV, 720 pages, Price 55 D.M. It is twenty-five years since the earlier edition of this classical work has appeared. The work is brought up to date by Wilhelm Treibs. Volume I is a historical intro- duction, discussion of production in the most modern producing areas, possible uses and physiological prop- erties of essential oils. Volumes II and !II will discuss analytical methods. The remaining volumes of the set of seven will cover the individual essential oils. Volume IV deals with the oils derived from cryptogams, gym- nosperms, monocotyledons and part of the dicotyledons including moni- miaceal. The mon. o.graphs .fo. llow a uniform pattern g•v•ng ong•n, extraction, characteristics and composition among the principal properties of each oil. Some monographs dealing with the more commercially im- portant oils are much longer than others. The data appear adequate. When completed, these useful volumes will enrich the knowledge of the volatile oils.--M. G. I)E- NAVARRE. ORGANIC COLLOIDS, by Bruno Jirgensons. D. Van Nostrand Co., Inc., Princeton, N.J. 1958. 900 pages, 6 X 9 inches, illustrated and indexed. Price $16.75. The book is divided into two parts, a general description of methods of preparation with a study of organic colloids and a "systematic survey of the most important classes of molecular and miceliar colloids" in a condensed