espiration is difficult, additional forces are
brought into play. Thus when the windpipe and bronchial tubes are
obstructed, as in croup, asthma, or consumption, many additional muscles
are made use of to help the lungs to expand. The position which asthmatics
often assume, with arms raised to grasp something for support, is from the
need of the sufferer to get a fixed point from which the muscles of the
arm and chest may act forcibly in raising the ribs, and thus securing more
comfortable breathing.

The visible movements of breathing vary according to circumstances. In
infants the action of the diaphragm is marked, and the movements of the
abdomen are especially obvious. This is called abdominal breathing. In
women the action of the ribs as they rise and fall, is emphasized more
than in men, and this we call costal breathing. In young persons and in
men, the respiration not usually being impeded by tight clothing, the
breathing is normal, being deep and abdominal.

Disease has a marked effect upon the mode of breathing. Thus, when
children suffer from some serious chest disease, the increased movements
of the abdominal walls seem distressing. So in fracture of the ribs, the
surgeon envelops the overlying part of the chest with long strips of firm
adhesive plaster to restrain the motions of chest respiration, that they
may not disturb the jagged ends of the broken bones. Again, in painful
diseases of the abdomen, the sufferer instinctively suspends the abdominal
action and relies upon the chest breathing. These deviations from the
natural movements of respiration are useful to the physician in
ascertaining the seat of disease.

212. The Nervous Control of Respiration. It is a matter of common
experience that one's breath may be held for a short time, but the need of
fresh air speedily gets the mastery, and a long, deep breath is drawn.
Hence the efforts of criminals to commit suicide by persistent restraint
of their breathing, are always a failure. At the very worst,
unconsciousness ensues, and then respiration is automatically resumed.
Thus a wise Providence defeats the purpose of crime. The movements of
breathing go on without our attention. In sleep the regularity of
respiration is even greater than when awake. There is a particular part of
the nervous system that presides over the breathing function. It is
situated in that part of the brain called the medulla oblongata, and is
fancifully called the "vital knot" (