66 4 NERVOUS SYSTEM. 



dictory results obtained by other observers by the fact that these contractions are very 

 marked during stomach- digestion, while they are wanting "when the stomach is entirely 

 empty, retracted on itself and in a measure in repose." According to the same author, 

 irritation of the splanchnic nerves, while it produces movements of the intestines, does 

 not affect the stomach. Judging from the tardy contraction of the stomach and the 

 analogy between the action of the pneumogastrics upon this organ and the action of the 

 sympathetic nerves upon the non-striated muscular tissue, Longet assumes that the motor 

 action of the pneumogastrics is due, not to the proper filaments of these nerves, but to 

 filaments derived from the sympathetic system. " This interpretation removes the sin- 

 gular physiological anomaly that an organ, the action of which is entirely removed from 

 the control of the will, should depend upon a voluntary, or cerebro-spinal nerve." This 

 explanation of the contradictory results of experiments and of the mechanism of the 

 action of the pneumogastrics upon the stomach seems entirely satisfactory and may be 

 accepted without reserve. 



Effects of Section of the Pneumogastrics upon the Movements of the Stomach. If the 

 pneumogastrics be divided in the neck in a dog in full digestion, in which a gastric fistula 

 has been established so that the interior of the organ can be explored, the following 

 phenomena are observed : 



In the first place, before division of the nerves, the mucous membrane of the stomach 

 is turgid, its reaction is intensely acid, and, if the finger be introduced through the fis- 

 tula, it will be firmly grasped by the contractions of the muscular walls. When the 

 pneumogastrics are divided, under these conditions, the contractions of the muscular walls 

 instantly cease, the mucous membrane becomes pale, the secretion of gastric juice is 

 apparently arrested, and the sensibility of the organ is abolished. Paralysis of the 

 stomach, etc., had been noted, long before the observations of Bernard ; but his experi- 

 ments upon animals with a fistulous opening into the stomach are the most striking. 



Notwithstanding the apparent arrest of the movements of the stomach in digestion by 

 section of the pneumogastrics, experiments carefully performed show that substances may 

 be very slowly passed to the pylorus, and that the movements, although they are greatly 

 diminished in activity, are not entirely abolished. This fact has been established beyond 

 question by the experiments of Schiff, who attributes the movements occurring after sec- 

 tion of the nerves to local irritation of the intramuscular terminal nervous filaments. 



Effects of Section of the Pneumogastrics upon Digestion, etc. When both nerves 

 are divided, in an animal in full digestion, the mucous membrane becomes pale and 

 flaccid, and the secretion of gastric juice is apparently arrested at once ; but, if the ani- 

 mal survive the operation for a day or two, a certain quantity of juice may be secreted as 

 the result of local stimulation, and digestion of a very small quantity of food, finely divided 

 and introduced into the stomach by a fistulous opening, may take place. A serious 

 difficulty in the digestion of large masses of food after division of the nerves is due to the 

 cessation of the movements of the stomach. It is stated that digestion may be to a cer- 

 tain extent reestablished, under these conditions, by galvanizing the peripheral extremi- 

 ties of the divided nerves. 



There is very little to be said with regard to the relations of the pneumogastrics to 

 the sensations of hunger and thirst. It would be very natural to infer, from the distribu- 

 tion of these nerves to the mucous membrane of the stomach, that they should be involved 

 in these sensations; but, in treating of this subject elaborately, in connection with ali- 

 mentation, we have shown that hunger and thirst really have their origin in the general 

 system, although the sensations are referred subjectively to the stomach and fauces, and 

 that, in all probability, the sensations persist after division of both pneumogastrics. 



With regard to the influence of the pneumogastrics upon absorption from the stomach, 

 we have also mentioned the fact that the passage of poisons from the stomach into the 

 blood-vessels may be retarded by section of the nerves, but is not prevented. 



Physiologists have given but little attention to the influence of the pneumogastrics 



