204 THE BIOLOGY OF THE ANIMAL 



Both living and alcoholic material should be used. 

 The latter will dissect more easily than the freshly- 

 killed specimens. Frogs may be killed in a few minutes 

 by being placed in a covered bowl with a wad of cotton 

 or a piece of cloth, upon either of which a few drops of 

 ether or chloroform have been poured. To preserve 

 them, open the body by cutting along the median ven- 

 tral line from the fore to the hind limbs. Open the 

 skull and the spinal canal by cutting away the bone 

 with scissors. Place the body in seventy per cent, alco- 

 hol for two or three days (being careful to see that the 

 abdominal cavity is kept open, so that the alcohol may 

 have access to the internal organs), then transfer for a 

 day or two to stronger alcohol. 



Two skeletons should be prepared, one having the 

 bones separated, the other having them connected by 

 the natural ligaments. The first one may be prepared 

 by cutting off the bones as much as possible of the flesh 

 of a fresh or alcoholic specimen, and soaking it for sev- 

 eral days in water or in water to which has been added 

 just enough potash to give the solution a decidedly slip- 

 pery feel. "Warmth will hasten the process. "When suffi- 

 ciently macerated, the flesh may be removed from the 

 bones with a tooth-brush. If it be desirable to keep the 

 bones of the fore and hind feet separate, wrap each of 

 those organs in a piece of fine cloth. After being cleaned 

 the bones may be bleached by laying them in a sunny 

 window where they will not be blown away. The sec- 

 ond skeleton should be made from a freshly killed frog, 

 though an alcoholic specimen will do. Cut off the flesh, 

 being very careful not to trim the ligaments too closely 

 at the joints, nor to cut away the cartilaginous portion 

 of the skeleton, especially that of the hyoid apparatus. 

 Throw the preparation into "Wickersheimer's fluid for a . 



