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WASHING BOTTLES, Squeeze Type, Polyethylene. Ofchemically resistant pure polyethylene, flexible, tough,lightweight and practically unbreakable. Squeezing pro-duces a steady, controllable stream or a few drops, as de-sired~, with delivery stopped instantly when pressure is re-leased.

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9823-F. Fittings, only, of polyethylene, consisting of vented screw cap and bentdelivery tube. For conversion of stock polyethylene bottles intoWashing Bottles.To fit Bottle, oz. ................ 4 8 or 16Cap size No. .............. ...... 2428Each ............................. .52.52Per dozen ....................... . 5.60 5.60 9823-F.10% discount from "dozen" price in assortments of 144 or more. Method of Packaging.

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announcinga new book!

Krueger's Principles of Microbiology

This new book for introductory courses in general microbiology orbacteriology, accurately brings the basic principles, concepts andviewpoints of the subject into sharp, clear focus. In a refreshingstyle of writing, the author covers the field of microbiology withoutplacing particular emphasis on any special branch of the subject,and keeps discussions abreast of all modern developments.The text is divided into nine parts. Parts 1 to 3 cover the

biology of bacteria-the latter part discussing enzymes and their role in microbial activities;the nutrition and respiration of microorganisms; environmental factors affecting their growth;and bacterial heredity and variability. After these divisions have been studied, the sequence oftreatment may be altered at the discretion of the instructor to suit his own plan of presentation.Part 4 explains microbiologic techniques and methods-laboratory study and culti-vation of microorganisms, inhibition and destruction of microorganisms by chemical andphysical means, and chemotherapeutic agents. The remainder of the book deals withapplied microbiology-soils, fermentations, foods, water and sewage, pathogens and plantpathology.Every effort has been made to provide the necessary background material to aid the studentin future studies. There are helpful study questions at the end of each chapter, and 143 superbillustrations. These illustrations-photographs, photomicrographs and line drawings-increasethe book's usefulness and further clarify the student's understanding of the subject matter.By WALTER W. KRUEGER, Department of Biology, Grand Rapids Junior College. 649 pages, 6" x 8", 143 illus-trations. New!-Ready in April.

W. B. SAUNDERS COMPANYWest Wauhlugft. Squre PhMladelhia 5

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SCIENCE, Vol. 1174

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USED Extra utility by removingAS 35X telescope portion and using asMICRO. 35 power microscope to in-SCOPE spect, dissect, etc. Excellent

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NON-ABSORBING BEAM-SPLITTING MIRROR - Latestdevelopment! Optically flat to 1,4 wave length. Size:1-15/16" x 2-15/16"-%"' thick. Reflects approximately 50%and transmits approximately 50%. No light is absorbed.Has a three-layered film which accomplishes non-absorption.

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EYE-PIECE MICROMETER-Imported! 19 mm. diameter. 10 mm. scale dividedinto 100 parts. Val. $5.00.Stock #30,035-W ..... .................... $3.50 Pstpd.STAGE MICROMETER-Importedl Rectangular glass slide with photographicseale 1 mm. long divided into units of 0.01 mm. Val. to $10.00.Stock #30,036-W ..... .................... $4.00 Pstpd.REVOLVING NOSEPIECE-Importedl Triple and quadruple. For Standard sizemicroscopes and objectives._

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TiltersMULTILAYER:-Bandwidth gen-erally less than 70 A. Peak trans-mission above 70%. Suppliedfrom stock for mercury green at5461 A, sodium D at 5890 A,hydrogen alpha at 6563 A, andlithium red at 6708 A, with var-iance from +30 A to -10 A.Available on longer delivery atmost wavelengths in the visibleregion. Provided in 2" and 1"squares, at $50 and $30.

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SCIENCE, Vol. 117

FOR DISTI IN AT HIGH VACUUM

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To MOIECUIAR STRUCTURE!

A simple, precision-built, high-efficiency unit whose normal fieldof distillation is among materialswhose molecular weights areabove 250, except for materialsof extreme heat sensitivity suchas some of the vinyl monomers.

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SCIENCE, Vol. 117

Recent Publications

CARNEGIE INSTITUTION OF WASHINGTON1530 P Street Northwest

Washington 5, D. C.Piibl.No.594 Smith, A. Ledyard, and Alfred V. Kidder.

Excavations at Nebaj, Guatemnala. WithNotes on the Skeletal MIaterial, by T. D.Stewart. 1951. Quarto, vii + 90 pp., frointis-piece, 90 figs. Paper, $5.25; cloth, $6.00.

597 Longyear, John M., III. Copan Ceramnics: AStudy of Southeastern Maya Pottery. 1952.Quarto, xiii + 114 pp., 118 figs., 3 maps.Paper, $5.25; cloth, $6.25.

Year Book 51, July 1, 1951-June 30, 1952. Reportson curreilt research from all the departmentsof the Institution. 1952. Octavo, xxxv + 20 +286 pp., 3 pls., 12 figs. Paper, $1.00; cloth,$1.50.

Subject lists in archaeology and anthropol-ogy; astronomy and astrophysics; botany, ecology,and climatology; chemistry and physics; embryol-ogy, genetics; geology and geophysics; history,economics, and history of science; literature;mathematics; mediciue; nutrition; paleontology;and zoology, or a complete catalogue will be sentupon request. Orders may be placed direct orthrough regular dlealers.

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Images up to 10 feet acrosseven under oil-immersed objectives

Because of the virtually solar intensity of the Scopi- , ;con's high-pressure mercury arc, you can project sharply Thdetailed images up to ten feet across even under oil- t .te@dy -immersed microscope objectives. The light's white color neith* w dsedemonstrates the various biological stains to their best *Ickms.advantage.

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9April 3, 1953

FUNDAMENTALS OF PHYSICAL SCIENCEBy Konrad Bates KrauskopfStanford University

New Third Edition694 pages, $6.00

In order to maintain a completely contemporary outlook and keep abreast of all recent advances, theauthor offers a fine revision of this excellent and extremely successful physical science survey text.Intended for the non-science student, it provides a thorough coverage of the main facts of astronomy,physics, chemistry, and geology.

These four fields are all treated from the point of view that they are parts of a unified gen-eral field of knowledge rather than stressed as distinct subjects. Superficiality is wholly averted throughselection of certain key topics of emphasis, then development of these topics with a rigor compar-able to that used in elementary courses in the specialized sciences. Throughout, it is principle ratherthan application which is stressed, for it is the author's intent that through knowledge of scientificmethods, the student will learn what a scientific problem actually is and the manner in which a scien-tist achieves solution.

In the revision, primary material on atomic nuclei, atomic energy, cosmic rays, andthe earth's interior have been brought up to date, and other, more minor revisions make the bookcomplete in modern methodology. New sections have been added, furthermore, on electronics, sili-cones, and recent theories about the origin of planets. Most of the half-tone illustrations are replacedfor great improvement, and new problems have been added.

The test is designed for great flexibility. Sections not essential to continuityhave been printed in smaller type, making the book adaptable to courses of differing lengths and varyingdegrees of difficulty. To further this convenience of teaching and presentation, problems which referto these less essential sections are marked with asterisks.

Here then is an excellent text to provide the student with ageneral understanding of the vital importance of science to the age in which we live, and to indicatethe manner in which it functions. The book is also of value to the student of specialized science forreview and background material in related fields.

Send for copies on approval

McGRAW-HILL BOOK COMPANY, Inc.330 West 42nd Street New York 36, N. Y.

SCIENCE, Vol. 11710