Note on either side of the median line in the dorsal region a pair of reddish glandular bodies (_the kidneys_). From each kidney trace a tube (_ureter_) posteriorly toward the region of the anus. The kidneys are the principal excretory organs of the body. The blood which flows through the delicate blood-vessels in the kidney gives up there much of its waste products. These pass out through small tubules of the kidneys into the ureters, which carry the wastes toward the anus. Along one side of each kidney may be seen a yellowish glistening mass, the _adrenal body_. In some of the specimens studied, the body cavity may be filled with thousands of little black spherical bodies. These are undeveloped _eggs_. They are deposited by the mother toad in the water in long strings of transparent jelly, which are usually wound around sticks or plant-stems at the bottom of the pond near the shore. From these eggs the young toads hatch as tadpoles and in their life-history pass through an interesting metamorphosis. (See Chapter XII.) TECHNICAL NOTE.--The teacher should be provided with several well-cleaned skeletons of the toad in order that the bones may be carefully studied. Boil in a soap solution a toad from which most of the muscles and skin have been removed (see p. 452). Leave in this solution until the muscles are quite soft and then pick off all bits of muscles 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. 2) 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 _vertebræ_, 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. Do the limbs attach directly to the axial skeleton? 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_, _tibio-fibula_, _tarsal_ bones, and _phalanges_ or _digits_. To what bones of the arm do these correspond? Determine the other principal bones of the skeleton by reference to figure 2. [Illustration: FIG. 2.--Skeleton of the garden toad.]