EFFECT OF VARIOUS METALLIC IONS 313 skin in vitrc, we noticed that when the skin of the animal had been fixed in the culture medium with a nickel clamp the growth of the fungus was checked. Secondly: in the course of our research aimed at finding self-sterilizing tissue, we became aware that tissues impregnated with silver nitrate, blackened by the sun, retained their antistaphylococcic property even after having been through the automatic laundry seven times (Fig. 1). Finally during the past year we have seen three patients suffering from contact eczema due to propyl or methyl p-hydroxybenzoate which are also used as preservative agents in numerous preparations of • .. :..•? %%'•g "•' '"' ..'".•'•,..:.:,!".:'..'..'.i'•'..,..!." :"• *•:•':"".• .,'.... ".::..." ':•:,. :: .•,:".:' ".:':.. :'. ............ , .... 2• '•' Figure. 1.•Tissue pieces after seven washings, on Staphylococcus aureus culture. Lift, control, right, previously impregnated with AgNO• solution and exposed to the sun. cosmetic and food products. Therefore we have thought it of value, from the thecretical point of view as well as practically, to examine the effect of certain metals on a pathogenic fungus of the guinea pig,/lchorion quinckeanum and on two molds that may be of concern to manufacturers of cosmetic products, Penicillium glaucum and/lspergillus niger. TECHNIQUE The culture medium used is BBL Sabouraud Maltose Agar.* The metal salts in the form of chlorides (except AgNOs) are added in aqueous solution while the medium is still warm and liquid. The concentrations are calculated to make the number of metallic ions equivalent and are given in milliatomgrams of the metal in one liter of the culture medium. The controls are xun on the culture medium alone and on the medium with CI ions (in the form ofHCl)that correspond to the several concen- tratio•:s. A week after culturing one records the first results and three weeks later one reads the final outcome. This affords the possibility to es- tablish a probable retarding effect on the growth as well as its inhibition. Three culture tubes are used for the test yet, for some slight divergen- cies the response has been the same in all three experiments. * Baltimore Biological Laboratory Co.

BOOK REVIEWS CHEMISTRY OF PLANT GUMS AND MUCILAGES, by F. Smith and R. Montgomery. Reinhold Publish- ing Corp., New York 22, N.Y. !959. 627 pages, illustrated and indexed. Price $18. The latest comprehensive treatise on the subject of gums, mucilages, derived products and synthetics. Seventeen chapters are required to discuss the subject starting with origin and ending with the physical properties of these substances. All the known facts are evaluated. Methods of analysis and separation are reviewed and criticized. In this reviewer's opinion the chapters dealing with synthetic gums are weak as well as the chapter dealing with the physical properties of gums. Some fine material has been published on gum viscosity but it is not mentioned. Both are minor faults in so fine a compilation. The descriptions and chemistry of the natural gums are very well done. Reference to this work will be made for years to come. Two appendices complete the book. The book is a must on any refer- ence shelf in the cosmetic indus- try.--M. G. DEN. HYDROGEN IONS, Vol. II, by H.T. S. Britton. D. Van Nostrand Co., Inc., Princeton, N.J. 489 pages, in- dexed and illustrated. Price $12.50. While pH is a tool every chemist uses daily, not all who use it under- stand what it is all about. The author, practically a pioneer in this field brings pH up to date, discuss- ing it in a practical way. His aim is threefold. First to correlate elec- trometric methods of testing sec- ond to show its importance in the practice of general chemistry and third to show how pH affects indus- trial processes. In this fourth edition, written over a span of 30 years, Britton uses 21 chapters to tell the reader about these facets of pH. This volume was used by the reviewer in a course of physical-chemical meth- ods and it undoubtedly will be used by many for some time to come. It is a useful reference.-- M. G. DEN. HYDROGEN BONDING, edited by D. Hadzi. Pergamon Press, Inc., New York 22, N.Y. 1959. 571 pages, illustrated and indexed. Price $17.50. There is much to be said for any book written by numerous experts in their respective areas. The pres- ent work however is the collection of papers on hydrogen bonding given at a symposium in Yugoslavia in 1957. That the work is authori- tative can be easily seen from some of the names of speakers at this symposium such as Pauling and Bernal. The material is of an "advanced" nature. Experiment and theory are both well covered. One will need a knowledge of French and German to understand some of the contribu- tions.---M. G. DEN. 352