RESPIRATORY SENSE. 481 



system what may appropriately be called a respiratory sense, 

 or, as it is called by the French, lesoin de respirer, which is 

 conveyed to the respiratory nervous centre and gives rise to 

 the ordinary reflex and involuntary movements of respira- 

 tion ; that this sense is exaggerated by any thing which inter- 

 feres with respiration, and is then carried on to the brain, 

 where it is appreciated as dyspnoea, and finally as the over- 

 powering sense of suffocation. An exaggeration of the 

 respiratory sense constitutes an oppression, which is referred 

 to the lungs. It has been demonstrated, however, that the 

 sensation of hunger, which is felt in the stomach, and of 

 thirst, which is felt in the throat and fauces, have their seat 

 really in the general system, and are instinctively referred 

 to the parts mentioned, because they are severally relieved by 

 the introduction of food into the stomach, and the passage 

 of liquid along the throat and oesophagus. It cannot there- 

 fore be assumed, from sensations only, that the sense of want 

 of air is really located in the lungs. The question of its seat 

 and its immediate cause is one of the most interesting of 

 those connected with respiration. 



Many physiologists accept the view of Marshall Hall, who 

 first accurately described the reflex phenomena, that the re- 

 spiratory sense is located in the lungs, is carried to the medulla 

 oblongata by the pulmonary branches of the pneumogastric 

 nerves, and is due to the accumulation of carbonic acid in the 

 pulmonary vesicles ; but there are facts in physiology and 

 pathology which are inconsistent with such an exclusive view. 



In cases of disease of the heart, when the system is im- 

 perfectly supplied with oxygenated blood, the sense of suffoca- 

 tion is frequently most distressing, though the lungs be unaf- 

 fected, and receive a sufficient supply of pure air. This and 

 other similar facts led Berard to adopt the view that the 

 respiratory sense has its point of departure in the right cavi- 

 ties of the heart, and is due to their disteiition as the result of 

 obstruction to the passage of blood through the lungs. 1 John 



1 Cours de Physiologic, tome iii., p. 523. 

 31 



