98 THE FROG 



and keep it free from dust. The edges of the glass plates 

 used in making the box may be bound together with passe- 

 partout. The best skeletons should be mounted by one or 

 the other of the above methods, but it is desirable to have 

 in addition some articulated skeletons mounted without cov- 

 ering, so that the bones may be demonstrated. An articu- 

 lated skeleton of a urodele is very useful for comparison. 



The cartilaginous cranium (see Holmes' Biology of the 

 Frog, Fig. 65) may be prepared after prolonged boiling 

 or maceration of the skull of a young frog, by carefully pick- 

 ing away the membrane 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 boil- 

 ing. Each set of bones should be kept in a separate box, or 

 in the case of a wet preparation, in a shell vial containing 

 alcohol. In preparing the disarticulated vertebral column 

 it is best to pass a wire through the neural canal before boil- 

 ing the bones, in order to make sure that the vertebrae 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 separated in order to enable the student to distin- 

 guish 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. For the arrangement of the bones of 

 the wrist and ankle, see Bourne, Comparative Anatomy, 



