310 INFLUENCE OF NERVES ON THE STOMACH. 



upon by the older physiologists, who found that glass balls and lead tubes, which 

 could be compressed only by a weight of 40 kilos. , were broken or compressed in the 

 stomach of a turkey. 



Influence of Nerves on the Movements. [The stomach is supplied by 

 the vagi and by the sympathetic, the right vagus being distributed to 

 the posterior surface, and the left to the anterior surface, of the 

 stomach.] The ganglionic plexus of nerve-fibres and nerve-cells (Auer- 

 bach's), which lies between the muscular coats of the stomach, must be 

 regarded as its proper motor centre, and to it motor impulses are con- 

 ducted by the vagi. Section of both vagi does not abolish, but it 

 diminishes the movements of the stomach. The muscular fibres of 

 the cardia may be excited to action, or their action inhibited by fibres 

 which run in the vagus (Nn. constrictores, et dilatator cardire), (v. 

 Openchowski). [If the vagi be divided in the neck, there is a short 

 temporary spasmodic contraction of the cardiac aperture. On stimulat- 

 ing the peripheral end of the vagus with electricity, after a latent 

 period of a few seconds, the cardiac end contracts, more especially if 

 the stomach be distended, but the movements are slight if the stomach 

 be empty.] 



Stimulation of the cceliac plexus causes movements in the stomach of 

 ruminants (Eckhard), perhaps indirectly through the effect upon the 

 blood-vessels. 



Local electrical stimulation of the surface of the stomach causes circular constric- 

 tions of the organ, which disappear very gradually, while the movement is 

 often propagated to other parts of the gastric wall. When heated to 25C., the 

 excised empty stomach exhibits movements (Calliburces). Injury to the pedunculi 

 cerebri, optic thalamus, medulla oblongata, and even to the cervical part of the 

 spinal cord, according to Schiff, causes paralysis of the vessels of certain areas of 

 the stomach, resulting in congestion and subsequent haemorrhage into the mucous 

 membrane. 



[It is no uncommon occurrence to find haemorrhage into the gastric mucous 

 membrane of rabbits, after they have been killed by a violent blow on the head.] 



158. Vomiting. 



Mechanism. Vomiting is caused by contraction of the walls of the 

 stomach, whereby the pyloric sphincter is closed. It occurs most 

 easily when the stomach is distended (dogs usually greatly distend 

 the stomach by swallowing air before they vomit) ; it readily occurs 

 in infants, in whom the cul de sac at the cardia is not developed. 

 It is quite certain that in children, this vomiting occurs through con- 

 traction of the walls of the stomach without the spasmodic action of 

 the abdominal walls. When the vomiting is violent, the abdominal 

 muscles act energetically. [The act of vomiting is generally preceded 



