THE FROG 71 
tangular glass case to prevent injury and keep it free from dust. 
The edges of the glass plates used in making the box may be 
bound together with passepartout. The best skeletons should be 
mounted by one or the other of the above methods, but it is desir- 
able to have in addition some articulated skeletons mounted with- 
out covering, so that the bones may be demonstrated. 
The cartilaginous cranium (see Holmes’ Biology of the Frog, 
figure 65) may be prepared after prolonged boiling or maceration 
of the skull of a young frog, by carefully picking away the mem- 
brane bones. 
In making disarticulated preparations of the skull, hands and 
feet each of these parts should be tied up in cheese cloth so that 
none of the bones will be lost during prolonged boiling. Each 
set of bones should be kept in a separate box. In preparing the 
disarticulated vertebral column it is best to pass a wire through 
the neural canal before boiling the bones, in order to make sure 
that the vertebre are kept in their proper position and order with 
reference to one another. 
The hand and foot should each be mounted by fastening the 
bones with liquid glue to a piece of stiff black cardboard or 
“mounting board.” The bones should be mounted in their 
natural position with reference to one another, but slightly sepa- 
rated in order to enable the student to distinguish the different 
elements. The bones of the wrist and ankle should be included in 
the preparations of the hand and foot respectively, and in the case 
of the hand the radio-ulna may well be added. Each preparation 
should be framed by covering it with a plate of glass of the same 
size as the cardboard (photographic negatives cleaned by boiling 
or treating with nitric acid to remove the film are excellent for this 
purpose), supported by strips of cardboard glued to the margins; 
the edges of the glass and cardboard may then be bound together 
with passepartout, used in the same manner as for a lantern slide. 
The permanency of such preparations will well repay the trouble 
of making them. 
Some of the long bones (e. g., the humerus and the femur) 
should be prepared by cutting, sawing or grinding them lengthwise 
so as to exhibit a longitudinal half of the bone with the interior 
cavity exposed. 
