THE SPINAL ACCESSORY NERVE. 563 



sequence of their contact. He says, that if the trachea be 

 divided and separated from the oesophagus, or if only the 

 oesophagus be tied, so that no food or secretion from above 

 can pass down the trachea, no degeneration of the tissue 

 of the lungs will follow the division of the pneumogastric 

 nerves. So that, on the whole, death after division of the 

 pneumogastric nerves may be ascribed, when it occurs 

 quickly in young animals, to suffocation through me- 

 chanical closure of the paralyzed glottis : and, when it 

 occurs more slowly, to the congestion and pneumonia pro- 

 duced by the diminished supply of air, by paralysis of the 

 blood-vessels, and by the passage of foreign fluids into the 

 bronchi ; and aggravated by the diminished frequency of 

 respiration, the insensibility to the diseased state of the 

 lungs, the diminished aperture of the glottis, and the 

 loss of the due nervous influence upon the process of 

 respiration. 



4. Respecting the influence of the pneumogastric nerves 

 on the movements of the ossophagus and stomach, the 

 secretion of gastric fluid, the sensation of hunger, absorp- 

 tion by the stomach, and the action of the heart, former 

 pages may be referred to. 



Physiology of the Spinal Accessory Nerve. 



In the preceding pages it is implied that all the motor 

 influence which the pneumogastric nerves exercise, is con- 

 veyed through filaments which, from their origin, belong 

 to them : and this is, perhaps, true. Yet a question, which 

 has been often discussed, may still be entertained, whether 

 all or a great part of the motor filaments that appear to 

 belong to the pneumogastric nerves are not given to them 

 from the accessory nerves. 



The principal branch of the accessory nerve, its external 

 branch, supplies the sterno-mastoid and trapezius muscles ; 

 and, though pain is- produced by irritating it, is composed 

 almost exclusively of motor fibres. It might appear very 



