VAGUS NERVE. yil 



The condition is probably one of reflex spasm that can be excited from the sensory 

 nerves of various areas (such as the teeth, the intestine, the skin) in the medulla 

 oblongata. Spasm of the dilators of the glottis and of other laryngeal muscles 

 also occurs. 



Irritation of the sensory nerves of the larynx, as is well known, causes cough. 

 If the irritation is intense, for example in cases of whooping-cough, the Lbers in 

 the laryngeal nerves, having an inhibitory influence upon the respiratory center, 

 may also be irritated; there occurs diminution in the respiratory frequency and 

 finally arrest of respiration with relaxation of the diaphragm; in the presence 

 of the most intense irritation, spasmodic arrest in expiration occurs, with closure 

 of the glottis, even for as long as fifteen seconds. The condition is an inhibitory 

 neurosis of the respiratory apparatus. Paralysis of the laryngeal nerves causing 

 alterations in the voice has already been considered. Paralysis of both recurrent 

 nerves, due, for example, to stretching in consequence of dilatation of the aorta 

 and the innominate artery, is attended with great waste of air as a result of the 

 fruitless efforts at phonation; expectoration is rendered difficult, and forcible 

 'cough impossible. In addition severe attacks of dyspnea may occur on exertion, 

 entirely like those that can be induced experimentally in animals. The increased 

 irritability of hysterical persons is associated with hyperesthesia and anesthesia 

 of the larynx, the upper air-passages, aphonia, a tendency to vomiting, a slow 

 and irregular heart-beat as signs of a neurosis of the vagus. Attacks of extreme 

 dyspnea lasting for from one-quarter of an hour to several hours have been referred 

 to irritation of the pulmonary plexus, which is supposed to cause spasm of the 

 bronchial muscles, bronchial asthma. Physical examination of the lungs discloses 

 in addition to rhonchi, no indication as to the cause of the severe attack. If the 

 condition is really one of spasm, this is probably in most instances of reflex origin, 

 the centripetal nerves of the respiratory passages, or of the skin (cold), or of the 

 genitalia (sexual asthma) being involved. Landois, however, was of the opinion 

 that in many cases considered as instances of asthma, the condition is one of 

 transitory paresis of the pulmonary nerves, exerting a stimulating effect upon the 

 respiratory center. The attack would, then, be a reproduction of the labored 

 breathing following section of both vagi. Whether the acute pulmonary emphy- 

 sema constantly observed in connection with this disease is due to irritation or to 

 paralysis of the muscular fibers in the lungs is as yet a matter of doubt. Ac- 

 cording to Biermer this is due to slight obstructions to expiration in the small 

 bronchi that are more readily overcome in inspiration than in expiration. Such 

 obstructions comprise catarrhal swelling of the mucous membrane, accumulation 

 of mucus or of blood, or spasm of the bronchi. 



Irritation in the distribution of the cardiac branches of the vagus may, by 

 direct excitation, cause attacks of diminished or even temporarily suspended con- 

 traction of the heart, together with a feeling of extreme prostration and of abolition 

 of the functions of life, occasionally also with pain in the precordium. Such 

 attacks may likewise be induced reflexly through irritation of the abdominal 

 viscera, in conformity with the percussion-experiment of Goltz. Landois first 

 analyzed these symptoms in 1865 on the lines of a physiological experiment and 

 designated them pneumogastric or reflex angina pectoris. Extirpation of the 

 larynx is occasionally followed by circulatory disturbances that may eventually 

 prove fatal. These are due to a persistent state of irritation of the laryngeal 

 nerves, eventually with extension to the vagus itself. Hennoch and Silbermann 

 observed slowing of the heart in children presenting irritative phenomena referable 

 to the stomach, and Landois, intermission of the heart-beat even in adults. Through 

 the same reflex action a derangement in the respiratory functions of the vagus 

 that Hennoch has designated dyspeptic asthma may be brought about. A similar 

 condition may be brought about reflexly also through other sensory nerves (uterine 

 asthma) . Rarely, intermittent paralysis of the cardiac branches of the vagus is 

 attended with marked acceleration of the heart-beat, up to between 160 and 240 

 beats, the rhythm^and the strength at times exhibiting great irregularity, and dysp- 

 nea in part setting in at the same time. Under such circumstances a careful 

 analysis is necessary in each case in order to determine to what extent irritation 

 of the heart-muscle, the heart-centers or the accelerator cardiac fibers are con- 

 cerned. Little of a trustworthy nature is known with regard to abnormal affec- 

 tions of the intra-abdominal fibers of the vagus. If the trunks of the vagi or their 

 centers are paralyzed, the most conspicuous symptom is labored, deep, slow breath- 

 ing, exactly as occurs after section of both vagi. 



