CONTACT CEPTORS 79 



been evolved to protect the lungs from the invasion of 

 foreign particles which might enter through the nose 

 and throat. The perfect adaptation of this mechanism 

 is manifested in the act of sneezing, which occurs when 

 the lungs are threatened by a foreign body approaching 

 through the nose. Breathing through the nose ceases 

 instantly that the foreign body may not be drawn 

 farther inward ; the mouth opens to take in a large 

 amount of air, which is suddenly and violently expelled 

 through the nose, effectively clearing the passage. 

 The protective action is further facilitated by the 

 simultaneous outpouring of mucus which, like tears, is 

 excellently adapted to carry off deleterious bodies. The 

 adaptive act of blowing through the nose is apparently 

 a recent development. 



To a foreign body in the larynx the adaptive response 

 is a cough. The regular respiration is inhibited, but 

 there is a cautious intake of air, followed by its violent 

 expiration through the partially closed vocal cords, so 

 that every portion of the upper mucous membrane is 

 subjected to a thorough searching pressure. This reflex 

 is of such value to the organism that it is ever active by 

 night as by day, being wholly abolished neither by sleep 

 nor by inhalation. anesthesia. 



Unlike the respiratory tract, the digestive tract is not 

 efficiently protected against the entrance of harmful 

 foreign bodies. The reflex responses to smell and taste 

 are excellent guardians of this region, however, for they 

 act as rigid censors of such deleterious matter as de- 

 cayed food, putrid flesh and excreta. The universal 

 repugnance of man and of some animals to the odor of 

 their own excreta is evidence that this is an ancient and 



