Care Use Research Articles

EFFECT OF TISSUE SIZE ON MEASUREMENTS OF SODIUM, POTASSIUM AND WATER CONTENTS OF ISOLATED RAT VENTRICULAR TISSUE.

DURING the course of experiments designed to examine the effects of inhalation anaesthetics on the sodium, potassium and water contents of isolated rat atrial tissue1, it was noted that the standard deviations of the sodium values were rather high. These values were thought to be unreliable and were therefore not reported. It was felt that part of the deviations in sodium values could be explained by the fact that uniform blotting procedures were not used on all tissues, thus removing variable quantities of sodium-rich bathing medium. Part of the difference could also be explained on the basis of contamination of the tissue or its digest from any number of sources, despite diligent care to use demineralized water and clean apparatus. Since the tissue was so small (about 50 mg) and its sodium content so small, it is easy to see that the slightest contamination would give erroneous results. As the experiments progressed, however, and greater attention was directed to the possibilities of contamination, the sodium values decreased and the standard deviations also decreased.

The Spiders of Wisconsin

The authors extend their thanks to Drs. Lowrie and Elder for the use of their collections, and to Sister M. Melanie and her enthusiastic students; to Mrs. L. Levi, Mr. R. Hunt, Miss R. Schiferl, Miss K. E. Dorney, and to many others who contributed spiders to this collection. The senior author is indebted to Prof. L. E. Noland and to Prof. N. C. Fassett of the University of Wisconsin whose encouragement made possible a collecting trip through Wisconsin in 1949. He was fortunate to examine Dr. D. C. Lowrie's collection, made in southeastern Wisconsin between 1938 and 1940. A small collection of spiders made by Dr. Wm. Elder about 1938 was found at the University of Wisconsin. Acknowledgement is due to Dr. A. Archer, Miss E. Bryant, Dr. B. J. Kaston, Mr. W. Ivie and Dr. H. K. Wallace, who have at various times helped with identifications; to Dr. R. V. Chamberlin for the loan of a specimen; to Mrs. C. Crocker for help with library work; to Dr. W. J. Gertsch who gave the senior author a great deal of time, help, and advicei. and loaned many spiders under his care for use in making drawings.

A Simple Pressure Balance

Precise pressure measurement in the range from 5 to 100 atmos. is quite a difficult problem. A set of high pressure mercury manometers is very unwieldy and difficult to use, while Bourdon gauges require frequent recalibration and are inherently inaccurate. The most likely solution for this problem is to use a simple piston-in-cylinder pressure balance, which, for these pressures and for accuracies of the order of 0.05 percent, can be relatively crude, and does not require excessively precise machining or care in use. A simple pressure balance was constructed for use in the pressure range from 25 to 35 atmos., and used for both pressure measurements and density change determinations. It proved perfectly satisfactory, giving pressures reproducible from day to day to about 0.01 atmos.

Care in Use of the Group O Card

Care in Use of the Group O Card

Children Born Out of Wedlock

Spaniard said of these children, Queer isn't it! Nature seems to know she must treat them better . . . because we shall treat them worse. Truly, society has accorded to children born out of wedlock treatment less kind than that accorded other children. A review of the plans for their care in use at different periods of time serves to place in relief the programs and the principles involved in the trends of today.

Physical Laboratory Experiments for Engineering Students

THIS book, prepared for use in the Polytechnic Institute of Brooklyn, is suitable for candidates for engineering degrees who have already pursued laboratory courses in physics. “Each experiment has been chosen because of its close connection with engineering work, and in many cases the theoretical result may be calculated from the constants of the apparatus with which that result obtained by experiment may readily be compared. As these two results approach to an equality the student gains confidence in the apparatus, confidence in the theory, and confidence in himself.” This is well said. There can be no doubt that many students lose not only confidence but also interest in physics when they find that owing to inefficient apparatus results of reasonable accuracy cannot be obtained. The experiments here described are well selected, and as apparatus of engineering design has been chosen, the equipment with ordinary care in use should continue to give sufficient accuracy. Special mention may be made of the apparatus for the study of the harmonic motion of a rotating system, which appears to be unknown to British instrument makers. The book is printed on good paper, and is well illustrated. Physical Laboratory Experiments for Engineering Students. Prof. Samuel Sheldon Prof. Erich Hausmann By. Part i. Mechanics, Sound, Heat, and Light. Pp. v + 134. (London: Constable and Co., Ltd., 1919.) Price 6s. net.