PRODUCTION OF SUGAR IN THE LIVER. 327 



Its mechanism it is difficult to explain. The irritation is 

 not propagated through the pneumogastric nerves, for the 

 experiment succeeds after both of these nerves have been 

 divided ; 1 but the influence of the pneumogastrics upon 

 gljcogenesis is curious and interesting. If both of these 

 nerves be divided in the neck, in a few hours or days, de- 

 pending upon the length of time that the animal survives 

 the operation, no sugar is to be found in the liver, and there 

 is reason to believe that the glycogenic function is arrested. 

 After division of the nerves in this situation, galvanization 

 of their peripheral ends does not affect the production of 

 sugar; but, by galvanization of the central ends, an impres- 

 sion is conveyed to the nervous centre, which is reflected to 

 the liver, and produces a hypersecretion of sugar. 3 These 

 questions will be referred to again, in connection with the 

 physiology of the nervous system. 



With regard to the influence of the sympathetic system 

 upon the glycogenic function, there have been few experi- 

 ments which lead to conclusions of any great value. Pavy 

 found that division of the sympathetic filaments accompany- 

 ing the vertebral arteries produced diabetes, but the opera- 

 tion was complicated by lesions of the vessels, which ren- 

 dered the results somewhat unsatisfactory. 8 



It has been observed that the inhalation of anaesthetics 

 and irritating vapors produces temporary diabetes; 4 and 

 this has been attributed to the irritation conveyed by the 

 pneumogastrics to the nerve-centre, and reflected, in the 

 form of a stimulus, to the liver. It is for this reason that 

 we should avoid the administration of anaesthetics in all ac- 

 curate experiments on the glycogenic function. In illustra- 

 tion of this fact, Pavy has collected twenty cases, in which 



1 BERNARD, loc. cit., p. 317. 



3 BERNARD, op. cz7., p. 324. It has been observed by Bernard that division 

 of the pneumogastrics in the chest, between the lungs and the liver, does not 

 affect the production of sugar (p. 328). 



3 PATY, op. tit., p. 87, et seq. 



4 BERNARD, op. oil., p. 327. 



