ABDOMINAL NERVES 543 



are stimulated there is no effect on the liver ; but when the stimulus is 

 applied to the central ends, the glycogenic processes become exagger- 

 ated and sugar makes its appearance in the blood and in the urine. 

 Bernard made a number of experiments illustrating this point, on dogs 

 and rabbits. The current employed usually was feeble, and it was 

 continued for five or ten minutes two or three times in an hour. In 

 some instances the stimulation was continued for thirty minutes. From 

 these experiments, it is assumed that the physiological production of 

 glycogen by the liver is reflex and is due to an impression conveyed to 

 the nerve-centres through the pneumogastrics. The inhalation of irri- 

 tating vapors and of anesthetics produces an increased glycogenic 

 action in the liver. The effects of irritating the floor of the fourth 

 ventricle, by which temporary diabetes is produced, have been con- 

 sidered in connection with the glycogenic action of the liver. 



Influence of the Pneumogastrics on the Stomach and Intestines. 

 Little or nothing is known in regard to the action of the pneumo- 

 gastrics on the spleen, kidneys and suprarenal capsules. The influence 

 of these nerves on the stomach and intestine will be considered under 

 the following heads : 



1. The effects of faradization of the nerves. 



2. The effects of section of the nerves on the movements of the 

 stomach in digestion. 



3. The influence of the nerves on the small intestine. 



Effects of Faradization. The stomach contracts under stimulation 

 of the pneumogastrics in the neck, not instantly, but after five or six 

 seconds. Stimulation of the splanchnic nerves, however, while it pro- 

 duces movements of the intestines, does not affect the stomach. Judg- 

 ing from the tardy contraction of the stomach and the analogy between 

 the action of the pneumogastrics on this organ and the action of the 

 sympathetic nerves on the non-striated muscular tissue, it has been 

 assumed that the motor action of the pneumogastrics is due, not to the 

 proper filaments of these nerves, but to filaments derived from the 

 sympathetic. This, however, is not exactly in accord with experimental 

 facts ; for it has lately been known that the pneumogastrics are the 

 excito-secretory nerves of the stomach and pancreas (Pawlow). 



Effects of Section of the Pneumogastrics on the Movements of the 

 Stomach. If the pneumogastrics are 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 mem- 

 brane of the stomach is turgid, its reaction is intensely acid and the 



