SCIENCE-ADVERTISEMENTS 



Lehz Microscope Stand '*A" with New 



Rotary Mechanical Stage Standard for 



Research in Leading Institutions. 



Leitz 

 Apochromatic Objectives 



In conjunction with 

 Universal nicroscope Stand " A" 



This series of objectives is now constructed under a revised 

 optical data and found to excel all others in flatness of field, high 

 degree of color correction and resolving power. Subjected to criti- 

 cal examination and comparison, they are selected by Government 

 Research Laboratories and for Research in the Leading Educational 

 Institutions. 



Our Universal Microscope, Stand "A," has been adopted as 

 Standard in these Institutions. This microscope features the Leitz 

 side fine adjustment, recognized as the most sensitive, at the same 

 time proving greatest stability. Our New Rotary Mechanical 

 Stage is supplied for critical research and photo-micrography, 

 making Stand "A" to represent the highest tyie of Research 

 Microscope obtainable. 



Specially reduced rate on Apochromatfor Duty Free 

 Importation. 



u. s. 



BRANCH 



NEW YORK 

 30 E. 18th St. 



INSTRUMENTS OF PRECISION 



For the Study of the Circulation 



JAQUET SPHYGMOCARDIOGRAPH for the simultaneous recording of three different tracinss in ad- 

 dition to the chronograph recoid. One tambour must always record the pulsation of the radial artery with 

 which it is in contact when the instrument is in position. The other two tracings may be from the carotid, 

 jugular, apex beat, etc., as desired. 



USKOF'"' SPHYGMOTONOGRAPH. The unique feature of this instrument is the simultaneous record- 

 ing of the blood pressure in millimeters of mercury together with the brachial pulse at varying pressures, and 

 one other tracing such as the carotid or jugular pulse or apex beat, and also time in J th seconds. In other 

 words, there are lour tracings upon the i aper, three of which are fixed by the limits of the apparatus, i. e., 

 blood pressure in millimeters of mercury, arterial pulsations at various pressures and time tracing, while the 

 fourth record may be taiien at pleasure from either the jugular vein, carotid artery or apex beat. 



MACKENZIE INK POLYGRAPH- Original English malce. This instrument records two simultaneous 

 tracings only, i. e., radial pulse and one other, such ascarotid. jugular, apex beat, etc., the great advantage being 

 the avoidance of smoked paper and the convenience and permanency of the inlc tracings which may be con- 

 tinued almost to any length from the long roll of paper supplied with the instrument. 



ELECTRO-CARDIOGRAPH APPARATUS. In this outfit the electro-motive force from the contract- 

 ing hi art muscle is measured by the use of the Einthoven String Galvanometer, an instrument of exceeding 

 sen.»ibility. A fine platinum or quartz thread constitutes the suspension of the galvanometer, the thread 

 being deflected to one side or the other as the electro-motive force from the heart varies in strength. 

 By the use of an arc lamp and a microscope system, the thread toeing of microscopic fineness, a photograph 

 of this thread is thrown upon a sensitized paper which is set in motion during the exposure. 



Send for our i 



illustrated pamphlet "Instruments of Precision for the Study of the Circulation 

 after Jaquet, Uskoff, Mackenzie and Einthoven" 



ARTHUR H. THOMAS COMPANY 



IMPORTERS AND DEALERS 



MICROSCOPES, LABORATORY APPARATUS AND 

 1200 WALNUT STREET, PHILADELPHIA, PA. 



CHEMICALS 



