The control of respiration

Abstract

The movements of respiration are carried out by voluntary muscles and ought to obey the laws of voluntary movement. One of the chief points in muscular action is the dependence of motor response on sensory impulses. Without the guidance of sensory impulses movements are ataxic. Just how ataxic or abnormal movements become depends on the extent of loss of sensory impulses and on the ability of the mechanism to guide itself by sensory impulses from other sources. These statements hold true in regard to the movements of respiration. It has long been known that a modified respiration results from cutting off the sensory impulses from the lungs by section of both vagi. Many investigators have, however, kept animals with divided vagi so that one cannot maintain that the vagi are essential to respiration. However, it was pointed out by one of us 1 a number of years ago that animals with vagi divided are not nearly as efficient in times of respiratory stress as is a normal animal. It was shown by Alcock, Einthoven and others that expansion of the lungs sets up electrical variations in the vagus, thus showing these sensory impulses actually exist. A number of years ago we 1 called attention to the alteration in respiration after section of the cord or division of the posterior thoracic roots. That impulses are set up in the joints of the thoracic cage every time the thorax expands may be shown by connecting the peripheral end of a cut intercostal nerve to a string galvanometer. There is an electrical variation each time the thorax is expanded. The respiratory center is thus informed of the position of the thorax as well as the position of the lungs.