97 



adjustable eye-lens. The division embraces a square of 5 mm, divided into 

 squares of 1.0 or 0.5 mm, as may be desired. 



Price : Code- word : 

 No. 14O: Eye-piece cross-line micrometer, in capsule . . Marks 5. . Pedregoso. 



When ordering please state whether the micrometer scale is required for 

 an ordinary or for a micrometer eye-piece. 



The Eye-piece Stops proposed by P. EHRLICH, No. 141, may be used for 

 counting the number of corpuscles within a field of known area, in a similar 

 manner as the eye-piece cross-line micrometers. These stops are provided with 

 square openings and are supplied in assorted sets having squares of 1, 2, 3, 4, 

 6, 8 and 10 mm. 



Price : Code-word : 



No. 141: Set of EHRLICH' s stops fy pieces) .... Marks 10. . Pedril. 



In the case of eye-piece cross-line micrometers as well as EHRLICH'S stops 

 - unless the latter are merely intended for verification of the quantities within 

 the same area - - it is necessary for each combination of objective and eye-piece 

 to ascertain, by means of stage micrometers, the actual surface values correspon- 

 ding to the various fields. 



EHRLICH'S stops being primarily designed for use in conjunction with micro- 

 meter eye-pieces (see p. 92), it should be expressly stated when ordering them if 

 they are to be used with other types of eye-pieces. 



Cross-line Stage Micrometers are, as a rule, supplied only in connection 

 with the appliance known as the * Counting Chamber (see Fig 55, a and b). 

 This latter consists of a cell of exact and uniform depth of 0.1 mm, the bottom 

 of which is ruled in squares (see Fig. 55, c). The most commonly used form of 



Fig. 55. THOMA'S Haemacytometer, No. 147. ( 2 / 3 Full Size.) 



a and b counting chamber, c a portion of the ruled bottom (magnified 30 X)> 



S M THOMA'S mixing pipette for red blood-corpuscles. 



, efena. 



