486 MATERIA MEDIC A AND THERAPEUTICS. 



Powerful reflex respiratory impulses are thus generated, and 

 pass out to the bronchial muscles and the diaphragm, which 

 are spasmodically contracted, interfering with the entrance of 

 air. 



Cough is essentially a physiological act, in itself highly 

 beneficial, which may require to be encouraged and increased. 

 Much more commonly, however, it is excessive, and becomes 

 one of the most distressing symptoms demanding relief in disease 

 of the chest. Expectoration may also be considered physio- 

 logical within certain limits, but will require to be modified 

 therapeutically when the quantity of the sputa is either ex- 

 cessive or deficient, or the quality rendered morbid by inspis- 

 sation or decomposition. Vomiting is closely associated with 

 cough and expectoration, which is not a remarkable circum- 

 stance, the two acts and their mechanisms being nearly allied 

 to each other, as we saw in chapter iv. 



fains, and sensations of irritation, tickling, necessity to cough, 

 " want of breath," tightness, oppression, suffocation, etc., are 

 always exceedingly distressing ; and, as they are among the 

 chief complaints of patients, demand relief if it can be afforded. 



IV. NATURAL RECOVERY. 



Nature's method of meeting an extraordinary or otherwise 

 morbid influence by destroying or removing it, is well seen in the 

 case of the respiratory system. Coughing and sneezing are 

 provisions for expelling any obstructing or irritating mass from 

 the air-passages ; and although apparently but of little service 

 in preventing the most serious kinds of lung disease, they may 

 really expel infective and other causes of morbid change much 

 more frequently than we suspect, just as they guard the nose 

 and the glottis from mechanically irritant particles. 



The second great natural method of relief which is seen 

 at work in this system is reaction or counter-action. The respira- 

 tory muscles respond to an obstruction in the passages by such 

 an increase of the force and frequency of their contraction as 

 will negative its action, and after a time they become hyper- 

 trophied if the obstruction persist. Dyspnoea or (better) 

 hyperpncea, is- the result, a large reserve of muscular force and 

 an almost unlimited power of hypertrophy sufficiently compen- 

 sating for the diminished size of the air-passages and air-current, 

 by increasing the depth and the frequency of breathing. The 

 same principle is at work in the catarrh, that is the hyperaemia 

 and secretion, set up in the air-passages or lungs on the en- 

 trance of a foreign body ; the mucous, serous, or even purulent 

 discharge all evidences of different degrees of reaction being 



