THE VISCERAL AND GUSTATORY APPARATUS 



239 



Vagus 

 ganglion 



Larynx 



Sympathetic 



lion 

 Postgangli- 

 onic neuron 



Fig. 113. Diagram of the nervous mechanisms of coughing and vomit- 

 ing. In the cough an irritation of the mucous membrane of the larynx is 

 transmitted to the nucleus of the fasciculus solitarius, from which the 

 tractus solitario-spinalis passes downward to the motor centers of the spinal 

 cord for the innervation of the muscles of the diaphragm, the abdominal 

 wall, and the ribs which cooperate in the production of the cough. In 

 vomiting, an irritation of the stomach is carried by sensory fibers of the 

 vagus to the nucleus of the fasciculus solitarius, from which the pathway is 

 as before to the spinal motor centers for the innervation of the diaphragm 

 and abdominal wall. In this case there is also an excitation of the dorsal 

 motor vagus nucleus, from which preganglionic fibers go out into the vagus 

 nerve for a sympathetic ganglion in the hypogastric plexus, from which, 

 in turn postganglionic fibers pass to the muscles of the stomach which par- 

 ticipate in the ejection of its contents. The diagram is suggested by one 

 in Ram6n y Cajal's text-book, though greatly modified. 



Attempts to localize the respiratory center in the mammalian medulla 

 oblongata more accurately have led to contradictory results. The old 



