6 4 



LABOR A TOR Y MICROSCOPES. 



[CH. II. 



have in it many other objects which are more easily seen, as the red blood corpus- 

 cles or particles of vegetation or dirt in the case of the blood preparation or of the 

 amoeba. 



ss 



61. 62. 



Figs. 61-63. Sectional Views of the two Forms of the Marker. 



Fig. 61. The simplest form of marker. It consists of the part SS zvith the 

 milled edge ( M). This part bears the Society or objective screzvfor attaching the 

 marker to the microscope. R. Rotating part of the marker. This bears the eccen- 

 tric brush (B) at its lower end. The brush is on a wire ( IV). This wire is eccen- 

 tric, and may be made more or less so by bending the wire. The central dotted 

 line coincides zvith the axis of the microscope. The revolving part is connected 

 with the " Society Screzv " by the small screw {S). 



Fig. 62. >SS, R, and B. All parts same as zvith Fig. 6/, except that the brush 

 is carried by a sliding cylinder the end view being indicated in Fig. 63. 



64. 



65. 



Figs. 64, 65, 66. Specimens Showing the Use of the Marker. 



In Fig. 64. a section of a series is marked to indicate that this section shows some- 

 thing especially well. In Fig. 65 some blood corpuscles showing ingested carbon 

 very satisfactorily are surrounded by a minute ring, and in Fig. 66 the lines of a 

 micrometer are ringed to facilitate finding the lines. 



