Fig. 259.—Brain of Frog.
Fig. 260.—Nervous System of Frog.
The brain of the frog (Fig. [259]) is much like that of a fish (Fig. [224]). The olfactory, cerebral, and optic lobes, cerebellum and medulla are in the same relative position, although their relative sizes are not the same. Compared with the other parts, are the olfactory lobes more or less developed than in a fish? The cerebral hemispheres? The optic lobes? The cerebellum? There is a cavity in the brain. It is readily exposed on the under surface of the medulla by cutting the membrane, which is there its only covering (Fig. [259]).
Fig. 261.—Position of legs in tailless (A) and tailed (B) amphibian.
Frogs and toads are beneficial (why?) and do not the slightest injury to any interest of man. If toads are encouraged to take up their abode in a garden, they will aid in ridding it of insects. A house may be made in a shady corner with four bricks, or better still, a hole a foot deep may be dug to furnish them protection from the heat of the day. A toad’s muzzle is not so tapering as a frog’s (why?), its feet are not so fully webbed (why?), and its skin is not so smooth (why?). In case of doubt, open the mouth and rub the finger along the upper jaw; a frog has sharp teeth, a toad none at all. The tadpoles of frogs, toads, and salamanders are much alike. In toad’s spawn the eggs lie in strings inclosed in jelly; frogs spawn is in masses (Fig. [248]).
Any batrachian may easily be passed around the class after placing it in a tumbler with gauze or net tied over top. It should be kept in a box with two inches of moist earth on the bottom. If no live insects are obtainable for feeding a toad, bits of moist meat may be dangled from the end of a string. If tadpoles are placed in a pool or a tub in a garden, the toads hatched will soon make destructive garden insects become a rarity.
Does a frog or a salamander have the more primitive form of body? Why do you think so? Salamanders are sometimes called mud puppies. The absurd belief that salamanders are poisonous is to be classed with the belief that toads cause warts. The belief among the ancients that salamanders ate fire arose perhaps from seeing them coming away from fires that had been built over their holes on river banks by travellers. Their moist skin protected them until the fire became very hot.