THE FROG 97 



Entire articulated skeletons require considerable time for 

 their preparation; good ones may be obtained from dealers 

 at reasonable prices. Articulated skeletons may be prepared 

 from specimens hardened in formalin, provided they have 

 not been preserved too long in the formalin; but the bones 

 must be cleaned by the tedious process of picking away the 

 muscle piecemeal with forceps. Formalin specimens are 

 undesirable for the preparation of disarticulated skeletons, 

 since it is difficult to make even tolerably clean preparations. 



Freshly-killed specimens are to be preferred when avail- 

 able, since the task of removing the muscles may then be 

 simplified by boiling. Remove the skin from the frog, 

 separate the fore-limbs together with the pectoral girdle, and 

 boil the parts for a few minutes in water, or better, in soap 

 solution prepared by heating ^nd thoroughly mixing the fol- 

 lowing : 



Hard soap 75 grams. 



Potassium nitrate (saltpeter) 12 grams. 



Strong ammonia 150 c.c. 



Distilled or soft water 2,000 c.c. 



For use, one part of this stock solution is diluted with three 

 parts water. If an articulated skeleton is desired, care must 

 be taken not to boil too long, as this will soften and weaken 

 the ligaments. Pick and brush away as much of the flesh as 

 possible, repeating the boiling if necessary. 



Complete articulated skeletons are best mounted in glass 

 jars containing alcohol, since in dry preparations the deli- 

 cate cartilaginous parts such as the hyoid apparatus and the 

 suprascapulas become shriveled. If for any reason a dry 

 preparation is desired, it may be mounted on a wooden base 

 and covered with a rectangular glass case to prevent injury 



