AMINOIDS for Culture Media SUPPLIES AMINO ACIDS in definite standardized amounts OFFERS nutritional nitrogen in immediately available form for bacterial utilization PREPARED in two forms 1. Aminoids (Biuret-free). (Beef or Casein.) In this second preparation 50% of the total Nitrogen is present in Descriptive letter-prices. Bibliography on request. The Arlington Chemical Company YONKERS, N. Y. FŒEİ Blood Counting Apparatus Each Blood Counting Apparatus is offered with our binding guarantee to conform to the specifications of the U. S. Bureau of Standards. The FLE Counting Chamber combines slide and supporting surfaces for the cover glass into one, elim Haemacytometer Complete with FEI Double Chamber inating the danger of loosening. The FLEI Counting Chamber is unique in design and characteristic of the following features: I. The construction entirely eliminates the cemented supporting surfaces for the cover glass. 2. The ruling produces increased visibility when in contact with solution. 3. The spacings of the ruling and the depth of the cell are guaranteed to be within the tolerance established by the U. S. Bureau of Standards, May 1, 1917. The FLE Counting Chamber is furnished in single or double form, with the following rulings: Pamphlet No. 0-131 will be furnished upon request 30 East E.LEITZ 18th Street Organized Under the Laws of the State of New York THE BROOKS' INDUCTOMETER In the Brooks' Inductometer is offered a compact form of variable inductance, with a self inductance range of 5 to 50 millihenrys, possessing the following advantages: 1. A fair degree of astaticism, which tends to eliminate errors due to stray field effects. 2. It is less expensive and at the same time fully as accurate as the AyrtonPerry instrument. 3. It occupies less space than the Aryton-Perry form. The instrument has a very nearly uniform scale, obtained by properly proportioning the coils. It may be used as a mutual inductance. It has a good ratio of maximum to minimum inductance (about 9 to 1) and also has as high a time constant as is consistent with good design and moderate size. The instrument is fully described in Bulletin No. 152, a copy of which will be sent upon request. For service that requires exceeedingly "fine" and uniform current regulation, we offer the following rheostats: Approximate Dimensions of 1 square Net 5" high $11.25 65 blocks thick 20" long 5 wide 6' high $22.50 46 60 blocks" thick 22" long 71" wide 3" square 7" high $36.00 60 blocks" thick 22" long 8" wide 4" square 9" high $90.00 *This rheostat is supplied with an extra movable terminal plate, as shown in the picture. JAMES G. BIDDLE 1211-13 ARCH ST., PHILADELPHIA Has three sets of walls. The outer wall receives the water a. By the expansion of the middle tube. A Kobe Condenser of this type with body 6" long is as efficient as a regular Liebig condenser, with body 35 or 40" long. Due to the expanded tube it may be used either as a regular condenser or as a reflux, being in this respect like an Allihn, but four or five times as efficient. It is especially recommended for liquids of low boiling point. On liquids of high boiling point its relative efficiency is somewhat decreased, though it is still much more efficient than other forms. Price of regular size with 6′′ body......$5.00 MANUFACTURED AND FOR SALE BY Prompt Shipment EIMER AND AMEND Headquarters for Chemical, Educational, and Industrial Laboratory Supplies Third Avenue, 18th to 19th Street NEW YORK, N. Y. PITTSBURGH OFFICE: 2011 Jenkins Arcade Biology Physics Have You Read These Four Important Books The Electron: Its Isolation and Measurement and the Determination of Some of Its Properties. By ROBERT A. MILLIKAN, Professor of Physics in the University of Chicago. Price $1.50, postpaid $1.60. The volume presents in a most interesting manner the results of the author's extensive research as a pioneer in this field. It describes some of the most significant properties of the elementary electrical unit, the electron, and discusses the bearing of these properties upon the two most important problems of modern physics; the structure of the atom and the nature of electro-magnetic radiation. Problems of Fertilization. By FRANK R. LILLIE, Professor of Embryology and Chairman of the Department of Zoology, the University of Chicago. Price $1.75, postpaid $1.85. Its purpose is to concentrate on the moment of fertilization itself, and to give a critical statement of the progress of investigation on this subject up to the present time. As the problem deals with the union of the male and the female sex elements which form the beginning of each individual's life-history, it has an important bearing on the problems of heredity. The Origin of the Earth. By THOMAS C. CHAMBERLIN, Head of the Department of Geology, the University of Chicago. Price $1.50, postpaid $1.60. The book sets forth the disclosures that led to the rejection, one after another, of the older views of the origin of our planet, the futile attempts then made to amend these or to build others upon the same foundations, the final rejection of these, and the construction of a radically new view based on a new dynamic foundation. Food Poisoning. By EDWIN OAKES JORDAN, Chairman of the Department of Hygiene and Bacteriology, the University of Chicago. Price $1.00, postpaid $1.10. This book presents in an interesting and readable manner the results of a thorough investigation into the extent of food poisoning, various kinds of food poisoning, articles of food most commonly connected with food poisoning, causes and prevention of food poisoning. THE UNIVERSITY OF CHICAGO PRESS 5811 Ellis Avenue CHICAGO, ILLINOIS Geology Chemistry Publications of Carnegie Institution of Washington The publications of the Institution now number over 350 volumes, the subjects including Anatomy, Archæology, Astronomy, Botany, Chemistry, Economics and Sociology, Embryology, Experimental Evolution and Heredity, Engineering, Folk-Lore, Geology, History, International Law, Literature, Mathematics, Medicine, Nutrition, Philology, Physics, Zoology. Classified and descriptive lists will be sent postpaid on application. Botany and Related Subjects In Press 248. BRITTON, N. L., and N. N. Rose. The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family. Quarto in 4 vols. Volume I will appear in June or July, 1919. It will be illustrated by 301 textfigures and 36 plates; of the latter, 28 are in colors. 286. WEAVER, JOHN E. The Ecological Relation of Roots. Octavo. 287. SPOEHR, H. E. The Carbohydrate Economy of Cacti. Octavo. 289. DOUGLAS, A. E. Climatic Cycles and Tree-growth. Octavo. 290. CLEMENTS, FREDERIC E. Plant Indicators: The Relation of Plant Communities to Conditions and Practices. Octavo. Published on June 20 Carnegie Pensions By J. McKEEN CATTELL Together with Extracts from Letters from Two Hundred and Fourteen College and University Professors, an Article on the History of the Carnegie Foundation by Joseph Jastrow, and the Reports of the Committee on Pensions and Insurance of the American Association of University Professors. Pages viii+253. Price, $1.50 Postpaid THE SCIENCE PRESS GARRISON NEW YORK KARPINSKI, BENEDICT and CALHOUN'S Unified Mathematics REPRESENTATIVE OPINIONS Professor E. E. DeCou, Univ. of Oregon: -It is a distinct contribution to the correlation of freshman mathematics. Professor J. R. Allen, Univ. of Minnesota:-I think that mathematics of the future will develop along this line, especially for engineers. Professor J. H. Tanner, Cornell Univ.: -It seems to me that a student who has carefully worked his way through this book will have a far better grasp of the subject of elementary mathematics than one who has studied the separate parts in the old way, and that he will also be able to use it far more effectively as a tool in his later work. Scientific American, New York:-In choice of illustrative and problem material an extraordinarily live and practical volume. Correspondence Invited D. C. HEATH & COMPANY Chicago Boston New York |