Even the lungs themselves depend upon the same source for nourishment, and if through imperfect breathing the assimilation becomes imperfect, and the lungs in turn become weakened, they are rendered still less able to perform their work properly, and so in turn the body becomes further weakened.

Every particle of food and drink must be oxygenated before it can yield us the proper nourishment, and before the waste products of the system can be reduced to the proper condition to be eliminated from the system.

Lack of sufficient oxygen means Imperfect nutrition, Imperfect elimination and imperfect health.

Verily, "breath is life." The combustion arising from the change in the waste products generates heat and equalizes the temperature of the body.

Good breathers are not apt to "take cold," and they generally have plenty of good warm blood which enables them to resist the changes in the outer temperature.
In addition to the above-mentioned important processes the act of breathing gives exercise to the internal organs and muscles, which feature is generally overlooked by the Western writers on the subject, but which the Yogis fully appreciate.
In imperfect or shallow breathing, only a portion of the lung cells are brought into play, and a great portion of the lung capacity is lost, the system suffering in proportion to the amount of under-oxygenation.