34 THE FROG ch. ii 



will be exposed, and, in front, the roof of the skull, which lies just 

 beneath the skin. Carefully dissect away the muscles along the middle 

 line of the back until the vertebral column is seen. Compare a prepared 

 skeleton and Fig 8, and make out the arches of the vertebrae. Between 

 the first of these and the back of the skull is a shght space : insert one 

 blade of the strong scissors into this, directing the points backwards, 

 and cut through the arch of the first vertebra, first on one, then on 

 the other side, and finally detach and remove the little piece of bone. 

 The neural canal will then be exposed, in which lies the spinal cord 

 (compare Fig. 6). 



Work backwards, cutting away the arches of the remaining vertebrae, 

 and you will find that the spinal cord ends behind in a thread-like pro- 

 longation. 



Next, using the scissors in the same manner, cut away, bit by bit, the 

 roof of the skull : two large bones — the fronto-parietals (see Figs. 8 

 and 9), forming a considerable part of the roof, can be more easily re- 

 moved by raising them up with the edge of a scalpel. Note the cavity 

 of the skull zxA its contained brain. 



General Structure of the Limbs.— With a strong knife, cut 



across one of the legs at about the middle of the thigh. Notice the 

 thigh-bone, muscles, and skin. Sketch. 



Now preserve your specimen in formaline ( i or 2 per cent. ), or spirit 

 (70 per cent.). 



