Fig. 149.—Diagram of brains of vertebrates; Olf. L., olfactory lobes; Cbr., cerebrum; Md. Br., midbrain (optic lobes); Cbl., cerebellum; Med. Ob., medulla oblongata; Sp. Cd., spinal cord. (From specimens.)

For a careful dissection of the mammalian nervous system a larger mammal, such as a cat or dog or rabbit, should be used. For guide use a text-book such as, for the dog, Howell's "Dissection of the Dog"; for the cat, Reighard and Jennings' "Anatomy of the Cat"; and for the rabbit, Parker's "Zootomy" or Marshall and Hurst's "Practical Zoology." Make a good preparation of the brain and preserve it for future use in some fluid like Fischer's fluid (see page [453]).

Technical Note.—Prepare a well-cleaned skeleton by boiling a specimen in a soap solution and thoroughly cleansing it (see p. [452]).

Note the very compact skeleton of the mouse. Note the closely sutured skull. How many cervical or neck vertebræ are there? The ribs are attached to the thoracic vertebræ. How many pairs of ribs? The bony thorax supports the shoulder-girdle and bones of the fore legs. The thorax is followed by a series of ribless vertebræ, the lumbar vertebræ, which in the posterior region of the body fuse with the pelvic girdle supporting the hind limbs. The body vertebræ are succeeded by the very much smaller caudal vertebræ. Compare the skeleton of the mouse with that of the bird; also with that of the toad. For directions for a detailed study of the skeleton see in Parker's "Zootomy" an account of the skeleton of the rabbit, pp. 263-286.

Fig. 150.—Diagram of vertebrate
eye; c, choroid; i, iris; l, lens; n,
optic nerve; r, retina; s, sclerotic.
(From Kingsley.)

Technical Note.—For the study of the eye (fig. [150]) the teacher should obtain the eye of some large mammal, as the ox or sheep, with which to make a class demonstration. The eye of a rabbit or cat can of course be used. For an account of the vertebrate eye see Parker and Haswell's "Text-book of Zoology," Vol. II. pp. 103-107. For a study of the ear use a bird or mammal, and see pp. 107-110 of the same book.