65. Tracing them from without inwards we see, then, that the various coverings afforded to the brain, the central organ of the animal life, seated in its vaulted cavity, are: 1. The tegument, consisting of the skin and of cellular and adipose membrane. 2. Beneath the tegument, muscles, in the forepart and at the vertex, comparatively slender and delicate; at the sides and posteriorly, thick, strong, and powerful (fig. XLIV.). 3. Beneath the muscles, a thin but dense membrane, termed the pericranium, lining the external surface of the cranial bones. 4. Beneath the pericranium, the bony substance of the cranium, consisting of two firm and hard bony plates, with a spongy, bony structure, called diploë, interposed between them (fig. XLIII. 2). 5. Immediately in contact with the inner surface of the bony substance of the cranium, and forming its internal lining, the dense and strong membrane, called the _dura mater_, not only affording a general covering to the brain, but sending firm partitions between individual portions of it (fig. XLVIII. _c._). 6. A serous membrane lining the internal surface of the dura mater, and reflected over the entire surface of the brain, termed the arachnoid tunic. 7. A thin and delicate membrane in immediate contact with the substance of the brain, descending between all its convolutions, lining all its cavities and enveloping all its fibres, called the pia mater. 8. An aqueous fluid, contained between the arachnoid membrane and the pia mater. Skin, muscle, pericranium, bone, dura mater, arachnoid membrane, pia mater, and aqueous fluid, superimposed one upon another, form, then, the covering and defence of the brain; so great is the care taken to protect this soft and tender substance. 66. The bones of the _face_ consist of fourteen, namely, the two superior maxillary or jaw-bones (fig. XXXVII. 5), the two malar or cheek bones (fig. XXXVII. 3), the two nasal bones (fig. XXXVII. 4), the two palate bones, the two ossa unguis (fig. XXXVIII. 8), the two inferior turbinated bones, the vomer (fig. XXXVII. 6), and the inferior maxilla or the lower jaw (fig. XXXVII. 7.) This irregular pile of bones is divided into the superior and inferior maxilla or jaws; the superior maxilla being the upper and immoveable portion of the face; the inferior maxilla being the lower and moveable portion of it. Besides these bones, the face contains thirty-two teeth, sixteen in each jaw. The bones of the upper jaw are united together by sutures, and the union is so firm, that they have no motion but what they possess in common with the cranium. The lower jaw is united by a distinct articulation with the cranium (figs. XXXIV. and XXXV.).