THE PNEUMOGASTRIC. 569 



fistula remained undigested. But Longet has found that if food be 

 introduced under these circumstances in small quantity, it may cause 

 the secretion of gastric juice, and may be finally digested and absorbed* 

 These results indicate that the functions of secretion and digestion in 

 the stomach are not immediately under the control of the pneumogastric 

 nerve, but that they become deranged after its section and practically 

 suspended, owing to the indirect influence of other causes. 



On the other hand, the muscular contractions of the organ and the 

 sensibility of its mucous membrane are both directly abolished by 

 division of the pneumogastrics. According to the observations of 

 Bernard, the finger, introduced into the cavity of the stomach through 

 a gastric fistula in the dog, is compressed with considerable force by 

 the walls of the organ ; but this pressure disappears completely if the 

 pneumogastric nerves be divided. The absence of muscular power in 

 the paralyzed stomach is of itself sufficient to account for the failure 

 of digestion when the influence of these nerves has been cut off. The 

 peristaltic action of the organ is essential to the digestive process, in 

 order to bring successive portions of the food in contact with its mu- 

 cous membrane 1 , and to cause the intimate admixture of the gastric 

 juice with all parts of the alimentary mass. The natural movement 

 and agitation of the food, by the action of the muscular coat, is no 

 doubt, also, an important stimulus to the continued secretion of the 

 gastric juice ; and when it no longer takes place, the digestive fluid will 

 necessarily be supplied in smaller quantity. It is evident, therefore, 

 that the pneumogastric nerves supply to the walls of the stomach a 

 certain amount of sensibility and a motor power, which are practically 

 essential to the process of digestion. 



Influence on the Action of the Heart. The pneumogastric nerve, as 

 already shown, gives off a number of filaments which are destined for 

 the cardiac plexus, and ultimately for distribution in the substance of 

 the heart. One or two of these filaments come from the superior 

 laryngeal branch of the pneumogastric, and immediately join the upper 

 cardiac nerve derived from the superior cervical ganglion of the sympa- 

 thetic. Several others are furnished by the main trunk of the pneumo- 

 gastric in the neck, which inosculate with each other and with the con- 

 tinuation of the upper cardiac nerve. The inferior laryngeal branch, in 

 its reascending course through the lower part of the neck, supplies so 

 many inosculating filaments to the same plexus of cardiac nerves that, 

 according to Cruveilhier, it appears in some instances to be distributed 

 in almost equal proportions to the larynx and to the keart. Finally 

 other small branches are supplied by the pneumogastric in the cavity 

 of the chest, which lose themselves at once in the cardiac plexus proper, 

 beneath the arch of the aorta. All the filaments, accordingly, which 

 are finally distributed to the heart through the cardiac plexus, originate 

 from the sympathetic and the pneumogastric nerves; and the entire 

 group is characterized by the frequent and intimate admixture of the 

 fibres derived from these two sources. A considerable proportion of 

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