CH. VI] 



INDICATOR OCULARS 



195 



with to be a really servicable instrument for the purpose in view; 

 and the mechanism is of thoroughly substantial character. I com- 

 mend this model to the notice of our opticians." 



Since its introduction by Tolles many opticians have produced 

 excellent demonstration microscopes of this type, but most of them 

 have not preserved a special 

 mechanism for fine adjustment. 

 With it one can demonstrate with 

 an objective of 6 mm. satisfac- 

 torily. It has a lock, so that 

 once the specimen is in the right 

 position and the instrument fo- 

 cused it may be passed around 

 the class. For observation it is 

 only necessary for each student 

 to point the microscope toward a 

 window or a lamp. 



A modification of this clinical 

 microscope was made by Zent- 

 mayer in which the microscope 

 was mounted on a board, and a 

 lamp for illuminating the object 

 was placed at the right position. 



308. Traveling Microscope. 

 For many years the French op- 

 ticians have produced most ex- 

 cellent traveling microscopes. The opticians of other countries 

 have also brought out serviceable instruments. For the needs of 

 the pathologist and sanitary inspector a microscope must possess 

 compactness and also the qualities which render it usable for nearly 

 all the purposes required in a laboratory. This instrument is a 

 type of much apparatus which has grown up with the needs of 

 advancing knowledge. 



309. Indicator or pointer ocular. This is an ocular in which 

 a delicate pointer of some kind is placed at the level where the real 

 image of the microscope is produced. It is placed at the same level 



A B 



Fig. 117 A, B. POINTER OCULAR 



AND FIELD WITH POINTER. 



FIG. 117 A. POINTER OR INDICA- 

 TOR OCULAR WITH A CAMEL'S HAIR 

 OP) STUCK TO THE OCULAR DIA- 

 PHRAGM AND EXTENDING OUT INTO 

 THE OPEN SPACE WHERE THE REAL 

 IMAGE is FORMED. 



FIG. 117 B. THE MICROSCOPIC 

 FIELD OF A BLOOD PREPARATION 

 WITH THE POINTER (P) DIRECTED 

 TOWARD A LEUCOCYTE. 



