CENTRAL SCIENTIFIC CO., CHICAGO. U. 8. A. 



169 



No. 3340. 



A B 



No. 3328. 



No. 3330. 



No. 8341. 



:;:ii4. COUNTING APPARATUS, Wolffhuegel's, for counting colonies of bacteria. Mounted on oak 

 base with large drawer; furnished with background plates, black and white; surface of the 

 plates is covered bv rulings 12 cm square $8.50 



.-!.;^5. RULED GLASS PLATE only for No. 3324 3.50 



3328. COUNTING PLATE, Frost's, printed in black with white lines, on good quality Bristol board. 

 The cross lines divide the figure into square centimeters. Four of these, just above the cen- 

 ter, are subdivided. The numbers, 40, 60 and 80, give the area of the disks bounded by the 

 circles just below them. The area of each sector, a and b, is one-tenth of the area enclosed 

 by its circle 10 



3330. COUNTING PLATE, Jeffer's, similar to No. 3328, but divided by concentric circles into equal 

 areas, which are subdivided by radii or segments of radii into smaller integral portions. The 

 numbers refer to the number of equal sections within the area enclosed by the circle just 

 beneath the number. Within the sectors a and b the areas enclosed between the three outer 

 circles are further subdivided into half-spaces. (See Journal of Applied Microscopy and 

 Laboratory Methods, Vol. I, No. 3) 10 



8344. MAGNIFIER for use in counting colonies of bacteria, magnifying 2^ diameters. Recommended 

 for use by the American Public Health Association. (See Standard Methods of Bacteriolog- 

 ical Analysis of Milk, for 1916, page 5) 1.00 



3336. CREMATOR, DeKhotinsky Electrically Heated, for flaming platinum loops. In inoculating cul- 

 ture tubes or making sputum smears the spattering occasioned by flaming the platinum loop 

 in the Bunsen burner flame is a source of great danger to the health of the operator. This 

 trouble is entirely done away with in the DeKhotinsky Cremator, in which the flaming of 

 the loops may be performed with perfect safety. The rapid flaming requires only a few 

 moments and is complete, since the bright ted heat to which the loop is subjected removes 

 all carbonized material. The apparatus consists of a tube of heat resisting material 4 inches 

 long by % inch inside diameter, closed at one end and wound with Chromel wire. This tube 

 is mounted in a neatly finished brass tube of 1% inches outside diameter, and the space 

 between the two tubes is filled with magnesia-asbestos mixture. This tube is mounted on a 

 base of asbestos board, fitted with binding posts for electrical connection and with a suitable 



support for the handle of the platinum loop. No A B 



For volts 110 220 



Each 10.00 11.00 



3340. CROSS SECTION CHART, made of extra quality blackboard cloth, with lines in white, accurately 

 spaced and permanent. Its surface takes crayon marks and permits their erasure as easily as a 

 blackboard. Can be rolled up when not in use. Size of ruled surface, 36x36 in 4.00 



3344. CROSS SECTION PAPER, one millimeter divisions with heavy centimeter ruling. In sheets 

 17x17 cm on transparent onion skin paper. Per quire .30 



3346. CROSS SECTION PAPER, accurately ruled, printed from an engraved plate. One millimeter 



divisions with heavier centimeter ruling; size 40x50 cm Per sheet .20 



Per quire 4.00 



3347. CROSS SECTION PAPER, same as No. 3346, continuous ruling in one millimeter divisions, 50 



cm wide Per yard .33 



3350. CROSS SECTION PAPER, ruled in ifoth inch divisions, size 16x21 inches Per sheet .08 



Per quire 1.50 

 33o2. CROSS SECTION TABLET, containing 75 sheets of paper metrically ruled with heavy lines every 



cm and light lines every 2 mm, with note ruling and marginal line on opposite side .18 



3354. POLAR CO-ORDINATE PAPER, printed from an engine divided plate, about 17 cm in diameter. 

 Per quire .45 



