INFLUENCE OF THE NERVES ON THE LIVER. 749 



of various stimulating fluids into the portal vein (Harley), and the in- 

 halation of acetone and benzine. Caustic potash and carbonate of 

 soda check the formation of sugar. (Pavy.) 



[Dr. W. A. Hammond, in his experimental investigations on the 

 ingestion of starch as an article of food, found, at the end of the fifth 

 day of his consumption of starch as his sole article of food, that sugar 

 appeared in his urine and continued during the remaining ten days of 

 experimentation. (Hammond : Physiological Memoirs. Philada. : J. 

 B. Lippincott & Co., 1863.) F. G. S.] 



An experiment, first made by Bernard, in which an artificial dia- 

 betes is produced, shows that certain parts of the nervous system in- 

 fluence the sugar-forming function (pp. 282, 312). It illustrates the 

 power of the nervous system over the nutritive and assimilative pro- 

 cessses, and may explain certain cases of ordinary diabetes. By pass- 

 ing a needle through the back of the occipital bone in the rabbit, and 

 irritating with its point, the floor of the fourth ventricle, from near 

 which the deep roots of the pneumogastric nerves spring, he produced 

 an artificial diabetes mellitus. Moreover, irritation of the cerebro- 

 spinal axis, from the cerebral peduncles down to the roots of the pneu- 

 mogastric nerves, on the sides of the medulla oblongata, increases the 

 formation of sugar in the blood, and gives rise to temporary diabetes. 

 On the contrary, division of the pneumogastric nerves in the neck, 

 that is, above the point where their branches to the lungs are given 

 off, appears to restrain the formation of sugar in the system ; section 

 of the spinal cord below the origin of the phrenic nerves, has appar- 

 ently a similar effect. 



It has been suggested that these effects are not direct upon the liver 

 itself but that, in the normal condition, a certain stimulus, perhaps 

 associated with the demand created by the process of oxidation going 

 on in the lungs, proceeds from those organs, through the pneumo- 

 gastric nerves to the medulla oblongata, and is thence reflected through 

 other nerves, to the liver, where it excites or regulates the glycogenic 

 action. On interrupting the continuity of this nervous chain, by 

 division of the pneumogastric nerves, the formation of sugar is checked. 

 Disturbances in the respiratory function, induced through the nervous 

 system or otherwise, may favor the formation of sugar and its accumu- 

 lation in the blood, and so produce diabetes. It is said, furthermore, 

 that division of the great splanchnic nerves, or of the sympathetic 

 nerves in the neck, increases the formation of sugar in the liver ; this 

 may depend, not on an increased formation of glycogen, but on the 

 increased quantity of blood then admitted to the liver, owing to dilata- 

 tion; through the action of the vasi- motor nerves, of the small arteries 

 of the abdominal viscera generally. The larger flow of blood through 

 the portal system and liver may change the glycogen already formed, 

 into sugar, more quickly than usual, and thus favor its more rapid 

 escape from the hepatic cells. This explanation may also apply to 

 the effect of irritation of the back of the medulla oblongata, in the 

 floor of the fourth ventricle, for the vasi-motor sympathetic nerve 



