in PRACTICAL DIRECTIONS 53 



completely calcined by heating to redness in a closed vessel, 

 when its animal matter is completely consumed and its 

 mineral matter left. Under these circumstances it becomes 

 very brittle, falling to pieces at a touch, and its appearance 

 is far more altered than by the removal of the mineral 

 matter. 



PRACTICAL DIRECTIONS. 



Preparation of the Skeleton. Kill a frog with chloroform (p. 31), 



open the abdomen as directed on p. 32, but without cutting the shoulder- 

 girdle, and remove the contained organs. Then, the frog being firmly 

 pinned down, remove the skin and gradually cut away the flesh from the 

 bones. In the case of the long bones of the limbs, it is best to cut 

 through the muscles near one end of the bone and then gradually to strip 

 them back towards the other end until the bone is exposed. The 

 process is facilitated by dipping the frog occasionally into boiling 

 water (maceration in cold water requires a considerable time) : this 

 softens the connective tissue by which the bones and muscles are bound 

 together, and thus allows them to be more readily separated. While at 

 work keep Fig. 8 before you, and be particularly careful not to injure 

 those parts of the skeleton which are made of cartilage (dotted in the 

 figure), and are therefore easily cut : the most important of these parts 

 are the hyoid or tongue-cartilage (J).hy\ lying in the floor of the mouth, 

 the omosternum (Fig. 12, Ep]^ the xiphistemum (fCn], and the supra- 

 scapula (Ffg. n, s.sc). Great care will also be required in cleaning 

 the bones of the hands and feet, since the fine cords or tendons which pass 

 to them from the muscles are very strong, and if pulled upon with much 

 force are sure to bring away the small toe-bones with them : they should 

 be separated as far as possible and then cut off, close to the bones, with 

 scissors. 



Keep all the parts of the skeleton together, avoiding separation of the 

 various bones until the general characteristics of the entire skeleton 

 have been made out : the only part which cannot be kept in connection 

 with the rest is the shoulder-girdle, together with the fore-limbs. 



Examination of the Skeleton- You should have two skeletons 



to examine one dried, after it has been thoroughly cleaned, and one 

 which has been kept from the first in spirit or formaline : the latter is 

 the more instructive (see also the paraffin method, given in Part II ; under 



