GENERAL BIOLOGY, New Third EditionBy PERRY D. STRAUSBAUGH, West Virginia University, and BERNAL R. WEIMER,Bethany College. This edition retains the "all life is one" approach of former editions,which made it a favorite beginners' text. The authors present a logical integration ofbiological facts, making possible the treatment of life as a unified concept. They developthe study of plants and animals simultaneously, and treat both as living things whichcarry on the same general life functions, with their differences appearing only in struc-ture and in the nature of machinery by whicb they carry on their work.

This edition stresses scientific method; the discussion of enzymes and their importancein all life processes has been brought up-to-date; the sections on respiration, genetics, andthe plant kingdom have been completely revised. April 1952. Approx. 828 pages.Prob. $6.00.

A NEW MANUAL for the BIOLOGY LABORATORYSecond Edition By BERNAL R. WEIMER and EARL L. CORE, West Virginia University.Three major revisions make the second edition more effective and useful: (1) outlinedrawings are bound in with appropriate text instead of being placed at the end; (2) spacefor student answers is left after each question; (3) all pages have been perforated andpunched for two- and three-ring notebooks. 1952. Prob. $2.75.

PRINCIPLES of GEOCHEMISTRYBy BRIAN MASON, Indiana University. This book summarizes the significant facts andideas concerning the chemistry of the earth, and synthesizes these data into a coherenttreatment of its physical and chemical evolution. April 1952. 276 pages. $5.00.

HETEROCYCLIC COMPOUNDS, Volumes III and IVEdited by ROBERT C. ELDERFIELD, University of Michigan. VOLUME III covers thePolycyclic Derivatives of Pyrrolei Polycyclic Systems with One Nitrogen Common toBoth Rings; Pyrindine and Related Compounds. April 1952. 442 pages. $12.00. VOLUMEIV covers the general principles and type reactions of Quinoline, Isoquinoline, and theirBenzo Derivatives. April 1952. 674 pages. $17.00.

ELEMENTARY ANALYSISBy KENNETH 0. MAY, Carleton College. A straightforward book designed for an inte-grated beginning course or a terminal course, Elementary Analysis gives the studenta good grasp of the logical nature of mathematics, the algebra of numbers, analyticalgeometry, and the simpler ideas of calculus by organizing all its topics around a few sig-nificant ideas. April 1952. Approx. 600 pages. Prob. $S.OO.

Send for on-approval copies today.

JOHN WILEY & SONS, Inc. 440 Fourth Avenue, New York 16, N.Y.

April 11, 1952 13

TWAErNTY-EIGHTH ANNUAL _IMEETING

SOUTHWESTERN DIVISION - AAAS

jointly with the

COLORADO-WYOMING ACADEMY OF SCIENCE

May 1-4 at the University of Colorado

Boulder, Colorado

Boulder is 25 minutes from Denver on this turnpike

For Information

On the meeting, write Frank E. E. Germann, University of Colorado

On Boulder and its environs, write the Secretary, Boulder Chamber of Commerce

SCIENCE, Vol. 11514

SOILS AND SOIL FERTILITYBY Louis M{. THOMIPSON, Iowa State College. AecGiraa-Hill Series il Agriculture. Ready inApr-il.

Designed for an elementary college course in soils, this text places particular emphasis on the forma-tion and classifications of soils, soil fertility and uses of fertilizers, and maintenance of organic matterand soil conserxation. The first six chapters deal with the physical, biological, and chemical propertiesof soils, and the formation and classification of soils. The remaining chapters deals with fertility andmanagement.

FUNDAMENTALS OF FRUIT PRODUCTION. New 3rd EditionBy- V\. R. GARDNER, U. S. Department of Agricuiltuire, F. C. BRADFORD and H. D. HOOKER, JR.MAcGraw-Hill Publications in the Agricultural Sciences. In press

Explains in an orderlN, systematic manner how the basic underlying principles of plant anatomy,morphology and physiology, and of soil science and climatology apply to the culture of fruit plants.Emphasis is on principles underlying growth and culture, not the details of practices. The treatmentdeals principally with the more common deciduous fruits. However, much illustrative material isdrawn from non-deciduous fruits and otlher crop plants. The scope is world-wide.

INVERTEBRATE FOSSILSBv RAYMOND C. MOORE, C. C. LALICKER. and A. G. FISCHER, University of Kansas. Ready inJutne

A w%ell-organized, comprehensive, descriptive guide to all important fossils. It is designed to serve asa text for college courses in Introductory Invertebrate Paleontolog-, and as a handbook for academicgeologists and practicing geologists in oil and otheri mineral industries. Over 400 line drawings illus-trate the more than 2,000 fossils described.

GEOLOGYBy 0. D. VON ENGELN, Cornell University, and KENNETH E. CASTER, University of Cincinnati.Ready in May

A basic text covering both physical and historical geology, this book starts with geologic phenomenafamiliar to the student, and, following this consideration of physical geology, presents the facts of his-torical geology as an outgrowth of the former. A strong narrativ e continuity is maintained throughoutwith logical sequences of chapters and topics.

Send for copies on approval

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

15Api-il 11, 1952

Wil rve ymu well-es they have served thsnds ofbiologists throughout the world for over thirty year. Theimportnce of thes items to human welfare far tran ndstheir montary value and TI Coleman & Bl Companyappreciates this responsibility by producing biological staithat are always d.pemNle. All of the stim in commonuse have been tested by the Biological Sin Commission.

C & B Products are distibuted byLaboratory and Physician Supply Ithwu

Throughout- th&-WOrwCatalog Upon Request. THE COLEMAN & BELL Co., Inc.

MafC Chemists, NOrwood, O., U$.A.

IJN FEU

FOR ROUTINE HIGH-CEIAn ultracentrifuge to concentrate, purify,and classify macromolecules and colloidalmaterials-proteins, viruses, enzymes,

chemical precipitates, etc.

Interchangeable angle-type rotors run invacuum chamber equipped with refrigera-tion for controlled rotor temperatures.

Automatic electronic controls govern theentire fast cycle of operation, monitor theself-balancing quiet 40,000-rpm electricdrive. Double armor-steel guard and inter-locks combine safety with dependability.

Sendfor compiete information onModelL Preparative Ultracentrifuge

SPECIALIZED INSTRUMENTSCORPORATION

605 O'NEILL AVE., BELMONT, CALIF.

SCIENCE, Vol. 115

TRYPTOPHAN-FREE

CASEIN

HYDROLYSATE

SPEIL CHEMICALS DIVIION

5 INC.14SO BROADWAY, NEW YORK 18, N. Y.

w

I L=

16

SCIENTISTS AND LABORATORY TECHNICIANS

Available In:Box of 3 lbs. - Price $ 1.95Carton (12 x 3 lb.) ea. 18.00Bag of 50 lb. lb. .40Barrel of 300 lb. .37

(slightly higher onPacific Coast)

If your dealer cannot supplyyou, write for literature and

samples.

Insist Upon the BEST.....

n OXA WORLD FAMOUS DETERGENT

No matter what you want to clean . . blood, encrusted pipettes,metalware, porcelain ware, machine parts, instruments, . . . no mat-ter how dirty or greasy they may be . ALCONOX will makethem sparkling clean, film-free, streakless.In soft or hard water, ALCONOX is equally effective. It actuallylifts off dirt, grime and grease faster than anything you have ever

tr-ied.SAVES ENERGY, SAVES TIME

Just wash and rinse. Toweling practically unnecessary. Economical too-one spoonful makes a gallon of active cleanser ready to

go to work on your toughest job.

Save time... labor...

eed Purina

Laboratory Chow

Busy ... then simplify your animal care withPurina Laboratory Chow. No mixing, no guess-

work ... one feed meets the nutritional require-ments of most laboratory animals. You will findit's clean and easy to feed in its convenientChecker form.

Tested by scientists for scientists, Purina Lab-oratory Chow provides an unchanging diet forlaboratory animals.

There's a Purina Dealer near you. See him todayfor fresh Purina Laboratory Chow, or write our

Laboratory Chow Department for information.

RALSTON PURINA COMPANY, St. Louis 2, Missouri

LAPURINA BLABORATORYJCHOWI7MMm----

April 11, 1952

&M,

imlIIfiEs III'mWillikilm I'llazi

.BMMRmzmpm

atimmum

17

RADIO-A (TIlVESTEROIDS

ImmediatelyAvailable

Estrone 16-C14Activity per mg.2.7 microcuries

Price per mg.$50.00

Progesterone 21-C14Activity per mg.2.25 microcuries

Price per mg.$40.00

Desoxycorticosterone acetate21-C14

Activity per mg.2.25 microcuries

Price per mg.$40.00

Form A.E.C. 374 andForm N.R.C.-C.R.247 (Canada) must ac-company each order.

For further information, write to:

~ 8.&&T&t&eo.P. 0. Box 247

Montreal Canada

WONDERFUL

RECORDINGS OF

121 BIRD SONGS

TWO albums of vinylite records bring 121 dif-ferent bird songs right into your home. These

recordings, made in the birds' natural habitats,feature North American warblers, birds of thewoods, fields, sea coasts and prairies.

A few of the 121 birds that sing for you on theserecords:

BluebirdStarlingLimpkin

Tufted TitmouseCanada WarblerRed-eyed Towhee

* An announcer identifies each bird before it sings* Attractively packaged in decorative albums that makewonderful gifts

Recorded for theAlbert R. Brand Bird Song Foundation,

Laboratory of Ornithology, Cornell UniversityVOLUME I

Six 10" records, 12 sides, $8.50 postpaidVOLUME 11

Five 12" records, ten sides, $10.50, postpaid

ALL RECORDS, FOR 78 R.P.M. MACHINES15% DISCOUNT TO SCHOOLS

MAIL THIS COUPON TODAY!r-------.-___

To: COMSTOCK PUBLISHING ASSOCIATES(Formerly Comstock Publishing Company,

a division of Cornell University Press)| 125 Roberts Place, Ithaca, New York l

Please send me .......... albums of Bird Songs Volume I@ $8.50 each, and. albums of Bird §ongs, Vol. Iume II @ $10.50 each, postpaid.

I Name .

Address .. .

| City . Zone .. State.-_ -- -_m.____ ____

April 11, 1952

WWOMM0.0

IdikAmAftAft Am Aft

19

a ~~PERSONNEL PLACEMENT-p a

1IaIIxIIIIItlg]ill]llIPOSITIONS WANTED ||||||||||||||||||

Bacteriologist: A.B., AI.S., two years study toward Ph.D. inpharmacology. Two years research in parasitology. Veteran, mar-ried, Sigma Xi, publications. Desire instructor or research associateposition. Available in July, 1952. Box 154, SCIENCE. 4/11

Botanist, 28, Ph.D. Desires academic position. General botany,ecology, taxonomy. Box 168, SCIENCE. X

Biochemist, Ph.D., desires responsible position. Sixteen years ex-perience planning, conducting, and directing research programs.Teachinig experience. Box 165, SCIENCE. X

Geologist, Ph.D., teacher college geology. long exerience, desiresteaching or laboratory position. Box 167, SCIENCE. X

Graduating physiologist, Ph.D., male, age 32, family, desires aca-demic-research position. Publications. Teaching experience. Refer-enices available. Box 161 SCIENCE. X

Microbiologist-biochemist. Ph.D. in physical chemistry, 6 yearspost-doctoral research in microbiology, biochemistry, plant physi-ology. Desires academic appointment with good research oppor-tunity. Box 164, SCIENCE. X

Positions Wanted:(a) M.S. (Vertebrate Zoology) ; two years, research assistant, de-partment of genetics, eastern university. (b) M.S. (Mycology-Microbiology); graduate course, medical mycology industrial my-cology; six years, research microbiologist, well kown company.For fturther information, please write Science Division, MedicalBureau, Palmolive Building, Chicago. X

Physiologist, Ph.D. in June, male, General, Comparative andMammalian Physiology, desires acadamic position with research op-portunities. Research in Endocrinology and General Physiology.

Plant Pathologist-Microbiologist, Ph.D., age 31, experienced inresearch and teaching; publications. Desires academic or industrialposition. Box 157, SCIEN-CE. 4/11

Physiologist: Ph.D. Age 36. Experienced teacher, active researcher(metabolism. enzymology). Outstanding scholastic record. NRCFellow. Medical school or University position. Box 162, SCI-ENCE. X

Zoologist, parasitologist. Ph.D. U. of M. Many publications. Broadteachiiig and research experience. Prefer combination teaching andresearch. T. Vergeer, 50 East 15, Holland, Michigan. X

Zoologist, biologist. Ph.D. Twenty years successful college teach-ing. Producer of man), graduate, medical students wants positionin stable progressive college. Box 160, SCIENCE. X

Zoologist: Ph.D., 15 years research and teaching experience: proto-zoology. parasitology, cellular physiology and growth. Numerouspublicationis. Desires university or medical school professorship.Box 1k45, SCIENCE. 4/4, 11

|||I||I|II|I|III||IIIII|||IIII||III|IIIII||'POSITIONS OPEN |||||11111111111111111111111111111111111111IEducational Representative-To contact teachers in medical andallied schools, colleges aind schools of nursing in Canada and Michi-gan, comprising provinces of British Columbia, Alberta, Saskatch-ewan Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia,New?oundland. College graduate 25-30 years old, science back-ground and teaching experience preferred. Knowledge of Frenchdesirable but not required. This is a full-time, salaried positionwith all expenses paid. Write P.O. Box 416, Phila. 5, Penna.,UT.S.A. 4/18

||||||||||||||||||||||||||||||||il!POSITIONS OPENElectron Microscopist-Physics or physical chemistry major withexperience in electron microscopy. Permanent. Salary open. Pleas-ant living and working conditions in expanding research group.Location-Ponca City, Oklahoma. State age, experience, educa-tion and salary desired in opening letter. Write direct to PersonnelRecords Division, Continental Oil Company, Ponca City, Okla-homa. X

Positions Open:(a) Director, new laboratory organized for toxicological inivestiga-tion of new organic compounds; M.D. or Ph.D. trained in phar-macology, biochemistry, biophysics or enzyme chemistry; East.(b) Industrial Hygienist; Bachelor's in chemistry, chemical engin-eering or biology required; new plant, South. (c) Senior Pharma-cologist, Ph.D. or M.D., qualified to initiate and develop phar-macological research program; important company; East. (d)Professor and Head, department of Physiology and Pharmacology;university medical school; $8500-$10,000. (e) Director of Re-search; Ph.D. or M.D.; should have flair for pure research; dutiesinclude some product development work; East. (f) Medical Editor;pharmaceutical company, East. (g) Biochemist or Chemical En-gmeer; research appointment; large industrial company; Midwest.S4-2 Science Division, Medical Bureau (Burneice Larson, Direc-tor) Palmolive Building, Chicago. X

Physiologist. Ph.D. or M.D. Research facilities available. Openingfor assistant professor and instructor. Send complete informationto Dr. E. W. Hawthorne, Head Dept. of Physiology, College ofMedicine, Howard University, Washington, D. C. 4/18

YOU can TELL and SELLover 32,000 top scientistshere . . . at a very low cost.

Your sales message in an ad this size costs only $43.75 at theone-time rate-less for multiple insertions. And the results!-well here's what one of the many satisfied advertisers inSCIENCE has to say . . .

"SCIENCE is consistently our most Profitablemedium. Business secured solely thru SCIENCE adshas been the backbone of our success in this field.""We carry a considerable amount of advertising invarious periodicals, but none is so productive of re-sults as SCIENCE."

Prove to yourself the effectiveness of SCIENCE in increasingyour Market, Sales, and PROFITS-send your "Copy" NOW-or write for further information and Rate card No. 27B.

C t ltweekly reaches over 32,000 top scientistsSCIENCE6 1515 Mass. Ave., N.W., Wash. S. D. C.

2(0 SCIENCE, Vol. 115

YOUR ad here reaches over 32,000 foremost scientistsin the leading educational institutions, industriallaboratories, and research foundations in the U. S.and 76 foreign countries-at a very low cost

CLASSIFIED: 15¢ per word, minimum charge $3.00. Use ofBox Number counts as 10 additional words.

DISPLAY: $17.50 per inch, no charge for Box Number.Correct payment to SCIENCE must accompany all ads.Insertion usually made 2 or 3 weeks after receipt of ad.SCIENCE * 1515 Mass. Ave.. N.W., Wash. S, D. C.

THE UNIVERSITY OF SYDNEYWALTER MERSH STRONG RESEARCH FELLOWSHIP

Applications are invited from persons qualified for appoint-ment to the Walter Mersh Strong Research Fellowship.The Fellowship is available for the purpose of conducting

original research in Papua in any of the biological, physicsor social sciences related to Papua or in Papuan History orLinguistics.The Fellowship shall be for one or two years' duration at

a salary of £800 to £1,100 per annum (plus cost of livingadjustment; males £182 and females £138 per annum)depending on age, experience and qualifications of the suc-cessful applicant.

In addition to the salary, grants not exceeding £500 perannum, according to requirements will be made to meetthe travelling and field expenses of the Fellow while engagedupon research work in Papua.

Full particulars of the conditions of award may be ob-tained from the undersigned, with whom applications closeon 30th June, 1952.

W. H. MAZE, Registrar

I

-Tie MARKET PLACE-BOOKS * SERVICES * SUPPLIES * EQUIPMENT

BOOKS ||||||||||llllllllllllllIIII

WANTED TO PURCHASE . . . Sets and runs. foreignOPERIODICALS and domestic. Entire

rie and smallerS and BOOKS collections wanted.WALTER 1. JOHNSON * 125 East 23rd St., New York 10. N. Y.

Your sets and files of scientific journalsare needed by our library and institutional customers. Please sendus lists and description of periodical files you are willing to sellat high market prices. Write Dept. A3S J. S. CANNER. INC.

_oston 19, Massachusetts

SCIENTIFIC BOOKS and PERIODICALS WANTEDComplee libraries-Sts and runs-ingl tidesPAl6s'o, please send us your want list$.

STECHERT - HAFNER, INC.31 East 10th St.. New York 3

YOU reach over 32,000 scientists inthese columns-at a very low cost

LOOKING FOR A PUBLISHER?Write for Free Booklet SC telling how we can publishyour book. All subjects considered. New authors welcome.

VANTAGE PRESS, Inc. 230 W. 41 St., New York 18.

FOODRESEARCH ~ RESEARCHLABORATORIES, INC.

Sws i~ForWe 1922IPhIpLH MOD.,*PruMe CONSULTATION

2-r~~~IleL Ose,FOD,DircoResourcth * Andlyms * Consulhalk

Biological, Nutritional, Toxicological Studies * ANALYSESfor the Food, Dr-ug and Allid Industries

48-14 33rd1 Sltrt, Lon Island Clty 1, Nt.Y

LOOKAROUND. . . notice the increasingnumber of satisfied advertisers using small-space ads regularlyin practically every issue of SCIENCE-proo that these smallads get results! If you have a product or service of interest toscientists, why not take advantage of this low-cost means of in-creasing your profits!

y'$ _~ 5

LABORATORY SERVICESin Biochemistry, Chemistry, Bacteriologyand Insecticide Testing

Vitamin assays including biologicalassaysfor vitamins A, D2 DV Eand K

Amino acid assays and biologicalprotein evaluations

Write for price schedule

WISCONSIN ALUMNI RESEARCH FOUNDATIONP. 0. BOX 2059 * MADISON 1, WISCONSIN

SUPPIES AND EQUIPMENT |

-~~~~~~~~~~~~~~~~~~~~~

l~ ~ r

SAF-T-GRIPBEADED EDGE

MICROSCOPE SLIDESNON-CORROSIVE * NON-FOGGING

* Smooth, diamond-processed beaded edge-won't slip orslide from hand-eliminates cuu from sharp edges.

* Made from water-clear glass-entirely free from flaws-guaranteed non-corrosive.

* Available in two types-plain or with frosted end foreasy marking.

* Economical-even as compared with ordinary sharp-edgedslides.

Write for prices, further information and samples.

PROPPER MANUFACTURING CO., INC.10-34 44th Drive, Long Island City 1, New York

April 11, 1952

I

YOUR ad here reaches over 32,000 foremost scientistsin the leading educational institutions, industriallaboratories, and research foundations in the U. S.and 76 foreign countries-at a very low cost

CLASSIFIED: 20¢ per word, minimum charge $5.00. Use ofBox Number counts as 10 additional words. Correctpayment to SCIENCE must accompany ad.

DISPLAY: Rates l'isted below-no charge for Box Number.Monthly invoices will be sent on a charge account basis

-providing satisfactory credit is established.Single Insertion $17.50 per inch

7 times in 1 year 16.00 per inch13 times in 1 year 14.00 per inch26 times in 1 year 12.50 per Inch52 times in 1 year 11.00 per inch

For PROOFS on display ads, copy must reach SCIENCE 4weeks before date of issue (Friday of every week).

11111111111111111PROIFESSIONA.L SERVICES t,'!lf!]llllll

A N N O U N C I N GPOST-GRADUATE INSTRUCTION IN HOMOEOPATHY

24th SessionPOST-GRADDUATE SCHOOL

American Foundation for HomoeopathyTime: J

toAu

t 8, 1952.Place: It tHo, Puua, Connecticut.Write to Foundation Secretary: Julia M. Green, M.D.1726 bye Savot, N.W. Washingio 6, D. C.

x_vx _AM- %'It lj.M.Ammmmmmll ]I=,

R`4

u

21

Ft oni II A

-The MARKET PLACE 1 GLASS ABSORPTION|IBOOKS * SERVICES * SUPPLIES * EQUIPMENT ELLS madeIFT

l|||||||||| |by SI IEn|

m Y Q *~~~~~RARE

IST~A IN S . COMMONSTARKMAN Biological Laboratory * Tororn to d-a |

MATCHED VISCOSITY TUBESJFor the air-bubble method of comparingviscosities. Simplest method of determiningviscosity on medium to heavy bodied liquids.Widely used in the varnish industry.

Write for leaflet V-5.

* HYPOPHYSECTOMIZED RATSShipped to all points via Air Express

For further information writeHORMONE ASSAY LABORATORIES, Inc. 8Ch8icago5, Il.

A/l AMINO ACIDS-natural, synthetic, unnatural,Rare Sugars, Biochemical Products, Reagents, NewPharmaceuticals in stock. Write or phone PLaza7-8171 for complete price list.

* BIOS LABORATORIES, INC. 17 West 60th Street,I_ __New__ York 23. N. Y.

0

Keep your copies of SCIENCE always available for quick,easy reference in this attractive, practical binder. Simplysnap the magazine in or out in a few seconds-no punch-ing or mutilating. It opens FLAT-for easy reference andreadability. Sturdily constructed-holds 26 issues.

This beautiful maroon buckram binder stamped in goldleaf will make a fine addition to your library. Only $2.75postpaid (personal check or money order please). Name,70¢ extra-year of issue, 40¢ extra. ORDER YOURS NOW!

SCIENCE . 1515 Mass. Ave., N.W., Washington 5, D. C.

Makers of Complete Electrophoresus ApparatusSCIENTIFIC APPARATUS

Klett-Summerson Photoelectric Colorimeters-Colorimeters - Nephelometers- Fluorimeters-Bio-Colorimeters - Comparators - Glass Stand-ards-Klett Reagents.

Klett Manufacturing Co.179 East 87 Street, New York, New York

P' VALUABLE IN STUDIES OF nSUGAR METABOLISM

Phosphorylated Sugars__ ~~~~~~~~Fructose-6-phosphate (barium salt), glucose-1-phosphate (dipotassium salt), and phospho-glyceric acid (barium salt), three vitallyimportant compounds in fermentation andenzyme reaction studies, are now availablefrom Schwarz Laboratories, Inc. Also immedi-ately supplied: Schwarz brand of fructosediphosphates (calcium, magnesium, and ba-rium salts), purity 85 per cent minimum.

Schwarz fine chemicals satisfy the exactingrequirements of products intended for use inbiochemical or clinical research.

Write for revised price list

LABORATORIES, INC.204 East 44th StreetNew York 17, N. Y.

2SCIENCE, Vol. 115

I22

~~ fg

TRACERLAB MAKES

OUTSTANDING

END-WINDOW

GEIGER TUBES

Tracerlab's Automatic Sample Changer allows laboratories makingradioassays on a large number of samples to obtain data faster, moreaccurately, and with greater reproducibility. Fully automatic radio-activity measurements on as many as twenty-five samples can be madeon this versatile unit without the attention of a technician. Results interms of elapsed time are printed on a tape by the Tracergraph, whichalso prints a corresponding sample index number.

In addition, half life measurements on short half life materials canbe made, or, with the E-25 Automatic Absorber Attachment, energyspectrum data on a particular sample can be obtained with the unitautomatically inserting absorbers of varying thickness over a fixedsample.

The complete unit for an automatic counting system consists ofthe Automatic Sample Changer, Shielded Manual Sample Changer(shown in position), Tracergraph Printing Interval Timer, and either theAutoscaler or Superscaler.Complete information on these instruments is contained in Tracerlab'snew 108-page Catalog. A copy will be sent on request.

- BERKELEY, CAL WASHINGTON, D. C.

NEW YORK, N. Y. - CHICAGO, ILLL

L~~~~~~~~~~~~ .I - .Aj

,. l1.

* The reports keep- coming in-.yes, the AO Scholar's Microscopedoes save time in teaching stud6tsmicroscopy.

MICROSCOPE CUTS TEACHING TIME This radically new idea in micro-s IIUCIOSCOE- CUTS TEACHING TIMEscopes has proven a boon to science

1. Easy to learn to Use. teachers. The built-in light source2. Single fosing control-fast assures permanently aligned

z | and precise. illumination and consequently better., 3. Factory-focused built-in lighto

Gsource limPhs time con- ~~optical performance with muchsource elimri@ates time con-Wsuming and freqety faulty less adjustment. Low overall height

,. ~~~substage adjustmentL.substage adjustments. increases comfort in operation.4. Reversed arm position gives* 4. Reversed arm position gives Locked-in parts reduce maintenanceclearer view of specimen

'stage, objectives, and costs. 'Spring-loaded' focusingdiaphragm openings. | mechanism protects slides against

Since we are currently supplying both military damage. See your AO distributorand civilian needs, instrument delivieris or write Dept. D2.

lk