198 PREPARATION AND MOUNTING 
complishing all that is desired. The tail is generally the 
. most transparent, and shows the circulation best; but in 
some of the newt larve the blood may be traced down to 
the very extremities if they are not too old. Mr. Whitney 
places the tadpole upon its back, by which means the heart 
and other internal arrangements may be seen. 
Amongst fishes also may be found subjects for the same 
purpose, but they seldom furnish such good examples as 
those before mentioned, because the blood-vessels are not 
nearly so abundant asin the foot of the frog, &c. The 
stickleback is, however, procurable almost in any place 
during the summer months, and may be laid in a shallow 
trough, loosely bound down as the tadpole. The tail may 
be covered with a piece of thin glass to prevent him curling 
it to the object-glass. The power needed for this will be 
about the same as with the other subjects; viz., a half to 
a quarter-inch object-glass. 
It is not absolutely necessary to go to reptiles or fishes 
for this curious sight, as some other animals serve very 
well. In the wings of the common bat may be found a 
good subject. These must be stretched out on something 
resembling the frog-plate before described, when those parts 
near to the bones will show the largest vessels very clearly. 
The ear of a young mouse is an illustration of the same 
phenomenon, but it is very difficult to fix it in a good 
position, as these animals are so very timid and restless. 
Amongst insects also the circulation may be seen by 
placing them in the cage, or live-box, so as to keep them 
still, but not to injure them by too much pressure. In 
certain larve it is particularly well shown, as in those of the 
day-fly and plumed gnat; but in some of these the blood is 
almost colourless. In the wings also of many insects this 
circulation is well seen, as in those of the common housefly ; 
but as these parts become dry in a few days, the subject 
should not be more than twenty-four hours old. 
Somewhat approximating to the forementioned pheno- 
menon, is the rotation (or cyclosis) of fluid in the cells, or, 
