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Chapter VII: The Four Methods of Respiration1695
Chapter VII: The Four Methods of Respiration
In the consideration of the question of respiration, we must begin by
considering the mechanical arrangements whereby the respiratory
movements are effected. The mechanics of respiration manifest through (1)
the elastic movements of the lungs, and (2) the activities of the sides and
bottom of the thoracic cavity in which the lungs are contained. The thorax
is that portion of the trunk between the neck and the abdomen, the cavity
of which (known as the thoracic cavity) is occupied mainly by the lungs and
heart. It is bounded by the spinal column, the ribs with their cartilages, the
breastbone, and below by the diaphragm. It is generally spoken of as “the
chest.” It has been compared to a completely shut, conical box, the small
end of which is turned upward, the back of the box being formed by the
spinal column, the front by the breastbone and the sides by the ribs.
The ribs are twenty-four in number, twelve on each side, and emerge from
each side of the spinal column. The upper seven pair are known as “true
ribs,” being fastened to the breastbone direct, while the lower five pairs
are called (false ribs) or “floating ribs,” because they are not so fastened,
the upper two of them being fastened by cartilage to the other ribs, the
remainder having no cartilages, their forward ends being free.