114 CLINICAL DIAGNOSTICS. 



bronchitis, pleurisy, pleurodynia, and in so-called "whooping- 

 cough" of dogs ; painless in chronic laryngitis. 



The force of the cough impulse depends upon 

 the vigor of the action of the expiratory muscles and the elas- 

 ticity of the lungs. Accordingly, the cough may be strong, 

 vigorous, or zvcak. It is weak if expiration is difficult or if 

 the patient is unable to cough vigorously : reduced, debilitated 

 animals, pulmonary emphysema, bronchitis, h\-drothorax ; or 

 if the expiration is painful: pleurisy, pneumonia, pleurodynia. 

 The cough is strong if the elasticity of the lungs is normal 

 and no pain attends the act. 



T h e d u ration of t li e cough i m p u 1 s e is 

 determined by the force with which the pulmonary air is held, 

 repressed by the closed glottis. If the pressure is great, the 

 glottis will be suddenly forced open and the cough will be 

 short. If the glottis is not completely closed (paralysis of the 

 arytenoid cartilage — roaring) or the repression of the air 

 causes pain (pleurisy), the cough is long — prolonged. 



The d c p f h an d ;;/ a g n i t u d c of the cough 

 depend partly upon the force and duration of the cough im- 

 pulse. The magnitude is influenced by the quantity of ex- 

 pelled air. We speak of a deep and a shalloi^< cough. 



The con g h sound is dependent upon the force of 

 the cough impulse, the tension of the vocal cords and the spe- 

 cial condition of the surface of the mucous membrane. The 

 sound may be loud, low, clear, dull, sharp, ivhistling, dense, 

 hollozv, loose, moist, dry. 



The ''ret u r n i in pulse'' of the cough ( Hus- 

 tenruecktstoss). Each cough is followed by a short, deep in- 

 spiration. If the glottis is not fully open at the moment this 

 inspiration takes place, the air rushing in causes the partially 

 stretched vocal cords to vibrate, causing a harsh, short, laryn- 

 geal stenotic sound to be emitted. It is heard in paralysis of 

 the larynx (paraplegia, hemiplegia) and in severe inflamma- 

 tory swelling. 



