Vlll 



SCIENCE— ADVERTISEMENTS 



AMERICAN STANDARD 



HAEMACYTOMETERS 



WITH LEVY COUNTING CHAMBER 



The Levy Counting Chamber was announced in November, 1916, was patented January 31st, 1917 



(U. S. Patent No. 1,214,331, and was awarded the Edward Longstreth Medal of 



Merit b tht FriiiHin Institutt. Philjdelphi i, December, 1917 



Wo. 29984. American Standard Haemacytometer with Levy Counting Chamber with double Nenbauer ruling 



THE LEVY COUNTING CHAMBER was the first dependable Haemacytometer Counting 

 Chamber made in the U. S. and continues to be superior in several important characteristics to any 

 chamber yet made either in Europe or America. 



It provides an increased visibility of ruling when the chamber is filled, unequalled by any ml- 

 ing of European make, and a new method of construction of the parallel form of cell (first sug- 

 gested by Biirker) which entirely avoids the cemented cell of the Thoma or Biirker construction 

 with the attendant danger of separation from the slide. 



The parallel or open form of chamber permits the filling of the ruled area on the cover glass 

 by capillary attraction after the cover glass is in position on the slide, and provides a more uniform 

 distribution of the corpuscles than is possible with the Thoma or circular form of counting 

 chamber which is entirely closed by the cover glass. 



The dimensions of the ruling and the depth of the cell are guaranteed to be within the toler- 

 ances established by the Bureau of Standards and, when so ordered, Counting Chambers are 

 furnished with Bureau of Standards certificate at an additional price. 



29991. American Standard Haemacytometer, complete with Levy Counting Chamber with Neu- 



bauer ruling, with two pipettes, in leather case 15.00 



29983. American Standard Haemacytometer, as above, but with Levy Counting Chamber with 



double Neubauer ruling 18.00 



29990. Levy Counting Chamber, with single Neubauer ruling 7.00 



29965. Levy Counting Chamber, with double Neubauer ruling 10.00 



Prices subject to change without notice 

 Copy of Sapplement No. 53, •'American Standard Haemacytometers" sent apon request 



ARTHUR H. THOMAS COMPANY 



WHOLESALE, RETAIL AND EXPORT MERCHANTS 



LABORATORY APPARATUS AND REAGENTS 



WEST WASHINGTON SQUARE PHILADELPHIA. U. S. A. 



