88 PHOTO-MICROGRAPHS. 
The manner in which this object was mounted 
for photography will serve to illustrate the general 
method of manipulation. 
First catch your fy. Kill it by compressing 
the thorax with forceps, and examine the head 
with a magnifying-glass, to see that it is uninjured 
and free from dust. If it is not perfect, renew 
the hunt. The dust may be removed by careful 
brushing with a camel’s-hair brush. Select a fly 
with a white forehead, for this reflects the light 
better than black; place a minute drop of glue, 
or of Canada balsam, in the centre of a perfectly 
clean slide; decapitate the fly and attach the 
head to the slide by means of this; in like manner 
attach a circular piece of black cloth or paper — 
dead black — to the opposite side of the slide. 
This serves as a background, and must be of such 
size that all direct light is prevented from enter- 
ing the objective, while as much light as possible 
passes outside of it to the Lieberkiihn. 
The object thus prepared is placed upon the 
stage of the microscope, and carefully centred in 
the optical axis of the instrument. 
The slightest speck of dust upon the object or 
upon the surface of the glass slide in the field of 
view, reflects the light strongly, and mars the 
beauty of the picture. 
