236 NEKVOUS SYSTEM. 



Bernard, who has presented by far the most satisfactory 

 explanation of this condition. 



Bernard found that the pulmonary lesion did not exist 

 in birds, although section of both nerves was fatal. It had 

 previously been ascertained that, in some animals, death 

 takes place with no alteration of the lungs. 1 "When the en- 

 trance of the secretions into the air-passages was prevented 

 by the introduction of a canula into the trachea, the carni- 

 fication of the lungs was nevertheless observed. "Without 

 detailing all of the experiments upon which the explanation 

 offered by Bernard is based, it is sufficient to state that he 

 observed a traumatic emphysema as a consequence of the 

 excessively labored and profound inspirations. Indeed, this 

 can be actually seen when the pleura is exposed in living 

 animals. As a result of this distention of the air-cells, the 

 pulmonary capillaries are ruptured in different parts, the 

 blood becomes coagulated, and the lungs are finally carni- 

 fied. This .cannot occur in birds, because the lungs are fixed, 

 and their relations are such that they are not exposed to ex- 

 cessive distention in inspiration. a 



There is no satisfactoiy explanation of the remarkable 

 changes in the respiratory movements that follow section of 

 the pneumogastrics. 



Sense of Want of Air. The pneumogastrics may regu- 

 late the respiratory acts, but they are not the medium 

 through which the sense of want of air (besoin de respirer\ 

 which gives rise to the reflex movements of respiration, is 

 conveyed to the nerve-centres. If it be true, as it undoubt- 

 edly is, that section of both pneumogastrics in the neck 

 modifies the number and the character of the respirations, 

 and that, after division of the nerves, galvanization of their 

 central ends arrests respiration, it is more than probable 



welche das Lungenparenchym nach Durchschneidung der Ner. vagi erleidet. 

 Gesammelte Beitrage zur Paihologie und Physiologic, Berlin, 1871, Bd. i., S. 80. 



1 BERNARD, Systeme nerveux, Paris, 1858, tome ii., p. 353. 



8 BERNARD, op. tit., p. 368. 



