ingcoluni chronmatography~' slto o e after.. wic amplng is

10 fractions of 20 cc each or 200 fractions of 1 cc each?

Break a given volume into many small fractions, ratherthan a few large ones, and you're bound to get sharper dif-ferentiation, higher resolution.

Stands to reason . .. but how? The manual "bi'rd-watching"method is tedious enough for a dozen-or-so collections: down-

| dt ~~~~right impossible when you need hundreds.It's no trick at all though when you mechanize fractiona-

|~~~~~tion with the Technicon automatic collector. You can run collec-10frac s of 20 cctions either by time-flow, or, if utmost resolution is required, by

s ~~~~~~drop count. Either way, all you have to do is mount the preparedt t ~~~column on the machine, set i't for the desired number (up to 200)

of samples of whatever volume you wish (from a single dropb|b ~~up to 28 cc). Then start it and go away.

thnCome back hours later (or next morning) and find the jobfeetalldone. Excess materialubeyond that required for the experi-Smentis automaticolly diverted to waste when the machine turnsmitself off on completion of the collection.

tion with theTechnicon a i ctollector

There's a lot more you should know about thistime-and-labor saving instrument. You'll find itin a brochure you can get by writing

TECHNICON CHROMATOGRAPHY CORP.Chauncey, New York

SCIENCE is published weekly by the AAAS, 1515 Massachuetts Ave., NW, Washington 5, D. C. Entered at the Lancaster, Pa., Post Office as second classmatter under the act of 3 March 1879. Annual subscriptions: $7,50; foreign postage, $1; Canadian postage, 50¢.

12 AUGUST 1955 267

ADVANCES IN EXPERIMENTAL CARIES RESEARCH-Edited by: Reidar F. Sognnaes, Harvard School of Dental Medicine

6 x 9 inches, 246 pages, 49 illustrations, index, clothbound, 1955

Price $6.75. AAAS Members' prepaid order price $5.75.A Symposium Volume of the American Association for the Advancement of Science

This is the first monograph devoted specifically to the information gained from research on theexperimental production and prevention of tooth decay in laboratory animals. Twenty distinguishedinvestigators, representing not only dentistry but also the basic sciences of anatomy, pathology, zool-ogy, biochemistry, nutrition and bacteriology, report and review pertinent experimental work. The bookhas been unusually well organized to represent a coherent sequence rather than a series of isolatedpapers, and the whole is summarized skillfully by the Editor in a final chapter, followed by a verydetailed subject and author index.

The importance and universality of the caries problem hardly need emphasis. Since clinical trialson humans are time consuming, costly and complicated, this animal work offers a most promisingapproach. Research reported here is encouraging in two respects. More precise knowledge has beengained regarding the long-suspected relationship between the oral environment and the production andprevention of tooth decay, and new light has been shed on various systemic factors contributing tothe development of caries-resistant teeth. The volume will suggest many further lines of researchtoward an ultimate solution of the problem.

CONTENTSProduction and Evaluation of Experimental Animal

Caries: A ReviewERLING JOHANSEN, University of Rochester, and PAUL H.KEYES, National Institute of Dental Research

Location of Experimental Caries on Different ToothSurfaces in the Norway Rat

ROBERT M. STEPHAN and M. RACHEL HARRIS, National Insti-tute of Dental Research

Genetic Factors in Experimental Rat CariesH. R. HUNT, C. A. HOPPERT, and S. ROSEN, Michigan StateCollege

Developmental Factors in Experimental Animal CariesJAMES H. SHAW and REIDAR F. SOGNNAES, Harvard Schoolof Dental Medicine

Dietary Factors in Experimental Rat CariesF. J. MCCLURE, National Institute of Dental Research

Salivary Factors in Experimental Animal CariesABRAHAM SCHWARTZ and DAVID WEISBERGER, Harvard Schoolof Dental Medicine

Endocrine Factors in Experimental Animal CariesWILLIAM G. SHAFER and JOSEPH C. MUHLER, IndianaUniversity

Intra-Oral Effects upon Experimental Hamster CariesSIDNEY B. FINN, CLARENCE E. KLAPPER, and JOSEPH F.VOLKER, University of Alabama

Oral Environmental Factors in Experimental RatCaries

FRANK J. ORLAND, University of Chicago and the ZollerClinic

Influence of Antibiotics on Experimental Rat CariesROBERT J. FITZGERALD, National Institute of Dental Research

Effect of Various Agents on Experimental Caries:A Resume

JOHN W. HEIN, University of Rochester

General SummaryREIDAR F. SOGNNAES, Harvard School of Dental Medicine

Mail your order now

To: AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE1025 CONNECTICUT AVENUE, N.W.WASHINGTON 6, D. C.

Please accept my order for:

O] Copies of Fluoridation as a Public Health Measure ...

Date ........................................................................

Price toRegular AAASPrice Members

................................ $4.50 $4.00

Copies of Advances in Experimental Caries Research ............................. 6.75 5.75My check or money order in the amount of $................................... isenclosed.

Name ............................................................................................................................................................................

Address ..........................................................................................................................................................................

City. Zone State

English Agents: Bailey Bros. & Swinfen, Ltd., 46, St. Giles High Street, London, W. C. 2

268SCIENCE, VOL. 122

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268 SCTENCE, VOL. 122

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12 AUGUST 1955 269

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WRITE FOR FOLDER NO. 301A

REFERENCES-As shown at the recent AAAS Na-tional Meeting in Berkeley in Decem-ber and The Federation Meetings inSan Francisco last April. It will bedemonstrated elsewhere in the future.

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