In adults there are two well-marked types of respiration, viz., the abdominal and the superior costal. The abdominal - met with in perfection in adult males - is the type in which the movements of inspiration and expiration are performed by the muscles of the abdomen and lower third of the chest. In superior costal respiration, on the other hand, the movements are most marked in the upper third of the chest. This form is best developed in healthy adult females.

In children the respiration is chiefly abdominal in type, irrespective of sex, and it is not until just before the age of puberty that the movements in the female change, becoming superior costal. Consequently, in estimating the number of movements per minute it is best to place the fingers lightly on the upper abdomen. The count should always be made by the watch, the most convenient time for the observation being while the child sleeps.

Soon after birth the number of movements per minute is 44, between the ages of two months and two years, 35, and between two and twelve years, 23. During sleep the frequency is reduced about twenty per cent.

Children under two years, while awake, breathe unevenly and irregularly; there are frequent pauses followed by hurry and precipitancy, and some of the movements are shallow, others deep. In sleep there is greater regularity. After the second year the movements become steady and even, like those of adults. All children, however, but particularly the very young, are subject to a great increase in the rapidity of respiration under the excitement of muscular movement and mental emotion.

Perfectly healthy children breathe through the nose, and so softly that it is necessary to place the ear close to the face to hear the breezy sound of the ingoing and outgoing air.

Examples of Variations in Disease. - Accelerated breathing occurs during the course of diseases attended by severe fever. Acute affections of the lungs are especially characterized by this alteration, and the more the breathing area is lessened the greater is the increase. Thus, in pneumonia, 60, 80 or 100 movements a minute are not at all unusual. To speak broadly, rapid breathing may be caused by an elevation in the body temperature, by an interference with the blood aeration, and by thoracic or abdominal pain.

Diminished frequency - the movements being reduced to 16, 12, or even 8 in the minute - is encountered in certain brain affections - namely, in chronic hydrocephalus, and the later stages of tuberculous meningitis. In such cases the rhythm may be greatly altered - a tidal form being assumed, in which the breathing ebbs and flows, beginning with an act which is scarcely perceptible or audible, gradually growing deeper until a full, noisy respiration is made, and then slowly subsiding into a period of absolute quiet, variable in its duration. This is termed Cheyne-Stokes respiration.

A dry, hissing sound, or a moist sound of snuffling, indicates partial obstruction of the nasal passages; oral respiration shows their complete occlusion.

Yawning, one of the modifications of the respiratory act, if it recur frequently, denotes great failure of the vital powers and is an unfavorable prognostic element.