144 THE MICROSCOPE. Oct. 
a star specimen for a cabinet. Exhibited with an inch 
objective it will excite wonder that so small a plant can be 
so beautiful and so complicated. 
Circulation of Blood.—Most books recommend the use 
of a frog’s foot for this purpose and give directions for 
accomplishing the purpose. The object may easily be 
attained with a small tadpole, lizzard, and with many of 
the larger water larvae. The latter will show the circu- 
lation all through the body. With the lizzard and tadpole, 
it may best be seen in the thin membranes of their tails. 
Allthat is necessary is to place the animal ina glass slip 
with a shallow cell and cover it. 
Opaque Objects.—The writer has known of amateurs 
who possessed microscopes for along time before learn- 
ing how to examine opaque objects. The specimen should 
have a dark ground, or if mounted transparent, an opaque 
slip, a piece of dark card board, or any other suitable thing 
to keep the light from below. Then, ifthe mirror swings 
above the stage, use that turning the concave mirror. 
The students’ lamp should be raised above the stage and 
_the lamp placed directly infront of it. Throw a bright 
spot on the object so that it will illuminate the part of the 
object focussed. Ifthe mirror does not swing above the 
stage, a bull’s-eye condenser must be used to illuminate 
the object. 
SCIENCE-GOSShe 
Examination of Milk.—Dr. William Royal Stokes, bac- 
teriologist to the health board of Baltimore, used the fol- 
lowing in the municipal laboratory in examining milk. 
When the milk examined is from one cow, or even when 
it is a mixed milk from many cows, it is centrifugalized 
for some minutes and then the sediment is spread out on 
a glass and stained. If many pus cells are found the 
specimen is rejected; but if there are only one or two pus 
cells in the field the specimen is passed. 
