SPASM OF THE LARYNX AND BRONCHIAL TUBES: ASTHMA.
Spasm of the opening in the larynx, the glottis (p. 355) as it is called, that affords a passage for air between the windpipe and upper parts of the throat, is not a very wide opening. It is also capable of being widened or contracted by muscles that surround it. It is when it is contracted to a narrow slit, and air forced rapidly through it, that voice is produced (p. 355). Now the contraction of muscles that pro duces the narrowing of the opening is effected by nerves, laryngeal nerves ; and if these nerves be stimulated in any way the contraction of the muscles, and the narrowing of the aperture of the glottis, will result. In spasm of the larynx the nerves are irritated in sonic way or other, the muscles suddenly contract, and the opening is greatly narrowed, so that the breath is drawn in with great difficulty. The narrowing may be so great that the opening is entirely closed, and then no air can be drawn in at all. The spasm may be due to inhaling very irritating vapour, or to some irritating substance finding its way into the larynx. We all know how, when something
we are eating or drinking " goes the wrong way," there is a sudden feeling of suffocation, great difficulty of drawing breath, accompanied by spasmodic attempts at coughing. The substance has entered the larynx and so irritated it that the glottis has spasmodically closed, while at the same time involuntary efforts to expel the offending substance are made. When the spasm yields there is often a long-drawn shrill sound, to which the term "whoop" is given, accom panying inspiration, due to the air rushing past the still narrow opening. Such spasms of the larynx are features in whooping-cough, so called because the whoop is specially character istic of the disease, and in other disorders. Sometimes spasm of the larynx is due to irri tation of one of the laryngeal nerves, caused by the growth of a tumour pressing on the nerve : it also occurs in hysteria. Child-crow ing (laryngismus striclulus) is a spasm of the larynx. It is discussed tinder DISEASES OF