THE GARDEN TOAD 25 



From these eggs the young toads hatch as tadpoles and in 

 their hfe-history pass through an interesting metamorphosis. 

 (See Chapter IX.) 



Technical Note. — The teacher should be provided with several 

 well-cleaned skeletons of the toad in order that the bones may be care- 

 fully studied. Boil in a soap solution a toad from which most of the 

 muscles and skin have been removed (see Appendix I). Eeave in this 

 solution until the muscles are quite soft and then pick off all bits of mus- 

 cles and tissue from the bones. If this is carefully done, the ligaments 

 which bind the bones will be left intact and the skeleton will hold 

 together. 



Note that the skeleton (fig. 9) consists of a head portion 

 which is composed of many bones joined together to form 

 a bony box, the skull; of a series of small segments, the 

 vertebrcB, forming the vertebral column, which with the skull 

 forms the axial skeleton; and of the appendicular skeleton, 

 consisting of the bones of the fore and hind limbs. Note 

 that the skull is composed of many bones joined together, 

 some by sutures, while others are fused. The anterior limbs 

 (arms) articulate with the pectoral or shoulder-girdle. The 

 arms will be seen to be made up of a number of bones placed 

 end to end. Note that the uppermost, the humerus, is 

 attached to the pectoral girdle, while at its lower end it 

 articulates- with the radio-ulna. At the lower end of the 

 radio-ulna is a small series of carpal bones which afford 

 attachments for the slender finger-bones, the phalanges or 

 digital bones. The bones of the leg are articulated with a 

 closely fused set of bones, the pelvic girdle. The leg-bones, 

 proceeding from the pelvic girdle, are named femur, tihio- 

 fibula, tarsal bones, and phalanges or digits. To what bones 

 of the a:rm do these correspond ? Determine the other prin- 

 cipal bones of the skeleton by reference to figure 9. 



Technical Note. — In a specimen which has been macerated for 

 some time in 20% nitric acid dissect out the nervous system. Place 

 the specimen in a pan, ventral side uppermost, and pii out. Carefully 

 pick away the vertebrae and" the roof of the mouth-cavity, thereby 

 exposing the central nervous system, which will appear light yellow. 



