SELECTION, ETC., OF OBJECTS FOR PHOTOGRAPHING. 103 
from floating about. It may be that mounting in 
glycerine jelly would be a good plan for the spores 
having some color, and this method would have 
the advantage of retaining them in position. 
EPITHELIAL CELLS. (ANIMAL.) 
Epithelial cells are to be obtained from the 
surface of mucous membranes by gently scraping 
them with a dull instrument, such as the blade of 
a pocket-knife, or by applying a thin glass cover, 
held with forceps, directly to the moist surface of 
the membrane. 
The flat cell with irregular outline, seen in 
Fig. 1, Plate IV., is from the mucous membrane 
of the human mouth. Detached cells of this kind 
will be found in great numbers in the saliva. A 
little of this fluid spread upon a thin glass cover 
and allowed to dry will furnish satisfactory fields 
for photography. Staining agents are required, 
to show the nucleus. In the example given, the 
agent used was methyl violet, — ordinary violet ink. 
The small, deeply colored spherical and rod-shaped 
bodies scattered over the surface of the cell and in 
the field around it are Bacteria. 
The ciliated epithelial cell, from the mouth of a 
frog, seen in Fig. 2, Plate III., was not stained, 
and indeed was still living, as shown by the 
active movement of the cilia, when the photo- 
graph was made. The small spherical body in 
contact with this cell is a mucus-corpuscle. This 
photo-micrograph gives a good idea of the spheri- 
