380 DISEASES OF BREATHING. 



place, with more or less blocking up of the bronchial tubes. I may explain 

 that the vaso-motor nerves are the nerves which, on becoming stimulat-ed, 

 cause contraction of the muscular coat of the blood-vessels. Whichever 

 theory we accept, we must, I think, regard asthma as a nervous disease which 

 is seldom if ever brought on by catarrh. 



The chief CAUSES of asthma are probably : bronchitis, foul air 

 in stables, and the breathing of air containing irritating vapours 

 or irritating particles. 



In order to warrant the decision that a case of difficulty of breath- 

 ing is due to asthma, we must prove the existence of these 

 paroxysms, independently of any external exciting cause, such as 

 work, and after more or less regular intervals of ease, during which 

 the breathing is normal, to a greater or less extent. The fact that 

 the breathing in asthma, though difficult, is not hurried, and that 

 it is slower in exj^iration than in inspiration, serves to distinguish 

 this disease from bronchitis and pneumonia. Also, in uncompli- 

 cated asthma there is little or no running from the nose, except, 

 perhaps, at the end of a paroxysm. 



TREATMENT. — One of the best medicines in this disease is 

 chloral hydrate, which may be given by the mouth in a dose of 3 

 drachms dissolved in a pint of water. If there be difficulty in this, 

 we may inject hypodermically (p. 633), 5 grains of morphia, or IJ 

 drachm of chloral hydrate ; or we might inject into the rectum 

 an ounce of chloral hydrate dissolved in a quart of w^ater. The pre- 

 cautions as to food and sanitation reoommended for broken wind 

 (p. 378) may be observed in cases of asthma. 



Asthma is a very serious unsoundness. 



Roaring. 



DEFINITION. — Roaring is a symptom of disease or malformation 

 which gives rise to noisy and more or less distressed breathing. 



VARIETIES. — The chief varieties of roaring are as follows : — 



1. The paralytic form, which is the cause of about 95 per cent, 

 of cases of roaring. 



2. Roaring from mechanical obstruction in the air j^cissages. 



3. Roaring from mechanical alteration of the sha^te of the air 

 2Jassages. 



4. Roaring from poison. 



Any of these varieties may be either chronic or temporary. 

 When the noise of roaring is shrill, it is sometimes termed 

 lohistling. 



NATURE AND CAUSES OF THE PARALYTIC FORM OF 

 ROARING. — ^Tliis disease is due to paralysis of one or both of the 



