at the base much thicker than
at the top or sides. The most important part of the brain is placed
here, completely out of the way of injury, unless of a very serious
nature. The base of the cranium, or skull, has many projections,
depressions, and apertures; the latter affording passages for the
nerves and blood-vessels.

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74. How many bones in the human body? How are they divided? 75-81.
_Give the anatomy of the bones of the head._ 75. How are the bones of
the head divided? 76. Describe the bones of the skull. 77. What is the
form of the skull? What does the base of the skull present?

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78. The bones of the cranium are united by ragged edges, called
_sut'ures_. The edges of each bone interlock with each other,
producing a union, styled, in carpentry, _dovetailing_. They
interrupt, in a measure, the vibrations produced by external blows,
and also prevent fractures from extending as far as they otherwise
would, in one continued bone. From infancy to the twelfth year, the
sutures are imperfect; but, from that time to thirty-five or forty,
they are distinctly marked; in old age, they are nearly obliterated.

[Illustration: Fig. 7. 1, 1, The coronal suture at the front and upper
part of the skull, or cranium. 2, The sagittal suture on the top of the
skull. 3, 3, The lambdoidal suture at the back part of the cranium.]

79. We find as great a diversity in the form and texture of the
skull-bone, as in the expression of the face. The head of the New
Hollander is small; that of the African is compressed; while the
Caucasian is distinguished for the beautiful oval form of the head.
The Greek skulls, in texture, are close and fine, while the Swiss are
softer and more open.

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78. How are the bones of the skull united? What are the uses of the
sutures? Mention the appearance of the sutures at different ages. What
does fig. 7 represent? 79. What is said respecting the form and
texture of the skull in different nations?

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80. In each EAR are four very small bones. They aid in hearing.

81. In the FACE are fourteen bones, some of which serve for the
attachment of powerful muscles, which are more or less called into
action in masticating food; others retain in place the soft parts of
the face.

[Illustration: Fig. 8. 1, The frontal, or bone of the forehead. 2. The
parietal bone. 3, The temporal bone. 4, The zygomat