362 



RESPIRATION. 



[CH. xxiv. 



sensory surfaces may also act as the " signal surface " for a cough. 

 Thus, a cold draught on the skin, or tickling the external auditory 

 meatus, in some people will set up a cough. 



The question has been discussed whether such a thing as a 

 stomach cough exists ; it has not been produced experimentally, 

 but there is no reason why irritation of the gastric mucous mem- 

 brane, supplied as it is by the vagus, should not cause the reflex 

 act of coughing. 



Sneezing. The same remarks that apply to coughing, are 

 almost exactly applicable to the act of sneezing ; but, in this 

 instance, the blast of air, on escaping from the lungs, is directed, 

 by an instinctive contraction of the pillars of the fauces and 

 descent of the soft palate, chiefly through the nose, and any 

 offending matter is thence expelled. 



The "signal surface" is usually the nasal mucous membrane, 

 but here, as in coughing, other causes (such as a bright light) will 

 sometimes set the reflex going. 



Hiccough is an involuntary sudden contraction of the diaphragm 



Fig. 324. Cheyne-Stokes respiration. (After "Waller.) 



causing an inspiration which is suddenly arrested by the closure 

 of the glottis, causing a characteristic sound. It arises from 

 gastric irritation. 



Snoring is due to vibration of the soft palate. 



Sobbing consists of a series of convulsive inspirations at the 

 moment of which the glottis is partially closed. 



Sighing and Yaivning are emotional forms of inspiration, the 

 latter associated with stretching movements of jaws and limbs. 

 They appear to be efforts of nature to correct by an extra deep 

 inspiration, the venosity of the blood due to inactivity produced 

 by ennui or grief. Their contagious character is due to sympathy. 



Among abnormal disturbances of the nervous mechanism of 

 respiration, the following diseases must be mentioned : laryn- 

 gismus stridulus, asthma, and whooping cough. 



Cheyne-Stokes respiration is due to rhythmical activity of the 

 respiratory centre. It reminds one somewhat of the Traube- 

 Hering waves due to a similar rhythmical activity of the vaso- 

 motor centre. It is seen in many nervous diseases and 



