24:4 NERVOUS SYSTEM. 



peripheral ends be galvanized, there is no effect upon the 

 liver ; but if galvanization be applied to the central ends, 

 the gljcogenic function becomes exaggerated, and sugar 

 makes its appearance in the blood and in the urine. Bernard 

 has made a number of experiments illustrating this point, 

 upon dogs and rabbits. The galvanic current employed was 

 generally feeble, and was continued for from five to ten 

 minutes, two or three times in an hour ; in some instances, 

 the irritation was kept up for thirty minutes. 1 From these 

 experiments, it is assumed that the physiological production 

 of sugar by the liver is reflex, and is due to an impression 

 conveyed to the nerve-centres through the pneumogastrics. 

 A very interesting and adroit experiment by the same ob- 

 server shows that section of the pneumogastrics between the 

 lungs and the liver does not affect the production of sugar. 

 This delicate operation is performed by making a valvular 

 opening in the chest, preventing the ingress of air by sud- 

 denly forcing the finger into the wound, and then introdu- 

 cing a long, delicate hook with a cutting edge, and dividing 

 the nerves, which may be reached by the finger in small 

 dogs, and feel like tense cords by the side of the oesophagus. 

 We have already noted, in another volume, 2 the fact ob- 

 served by Bernard and by Pavy, that the inhalation of irri- 

 tating vapors and of anaesthetics produces a hypersecretion 

 of sugar. 



The remarkable effects of irritating the floor of the fourth 

 ventricle, by which we can produce temporary diabetes, have 

 been considered fully in connection with the glycogenic 

 function of the liver. This effect is not due to a direct trans- 

 mission of the irritation to the liver through the pneumo- 

 gastrics, for the phenomena of hypersecretion are observed 

 in animals upon which this operation has been performed 

 after section of both pneumogastrics in the neck. It is prob- 



1 BERNARD, Lemons de physiologic experimentale, Paris, 1855, p. 325 ; and, 

 Systeme nerveux, Paris, 1858, p. 437, et seq. 

 8 See vol. iii., Secretion, p. 327. 



