SOURCES OF GLYCOGEN. 353 



chloride, and (?) CO. But congestion of the liver produced in other ways appears 

 to cause diabetes e.g., after mechanical stimulation of the liver. To this class 

 belongs the injection of dilute saline solutions into the blood (Bock, Hoffmann), 

 whereby either the change in form or the solution of the coloured blood-corpuscles 

 causes the congestion. The circumstance that repeated blood-letting makes the 

 blood richer in sugar may, perhaps, be explained by the slowing of the circulation. 

 [Injection of a solution of a neutral salt into a ligatured loop of the small intestine 

 sometimes causes mellituria (M. Hay).] 



Continued stimulation of peripheral nerves may act reflexly upon 

 the centre for the vaso-motor nerves of the liver. Diabetes has been 

 observed to occur after stimulation of the central end of the vagus (Cl. 

 Bernard, Eckhard, Kiilz, Lobeck), and also after stimulation of the 

 central end of the depressor nerve (Filehne). Even section and subse- 

 quent stimulation of the central end of the sciatic nerve causes diabetes 

 (Schiff, Kiilz, Bohm and Hoffmann, Froning), and thus is explained 

 the occurrence of diabetes in people who suffer from sciatica. 



According to Schiff, the stagnation of blood in other vascular regions of the 

 body may cause the ferment to accumulate in the blood to such an exent that 

 diabetes occurs. The glycosuria that occurs after compression of the aorta or 

 portal vein may perhaps be ascribed to this cause, but perhaps the pressure pro- 

 duced by these procedures may paralyse certain nerves. According to Eckhard, 

 injury to the vermiform process of the cerebellum of the rabbit causes diabetes. 

 In man, affections of the above-named nervous regions cause diabetes. 



Theoretical. In order to explain the more immediate cause of these pheno- 

 mena several hypotheses have been advanced : 



(a.) The liver glycogen may be transformed unhindered into sugar, as the blood 

 in its passage through the liver deposits or gives up the ferment to the liver- 

 cells (see above). So that the normal function of the vaso-motor system of the 

 liver, and its centre in the floor of the fourth ventricle, may be regarded as, in a 

 certain sense, an " inhibitory system" for the formation of sugar. 



(b.) If we assume that under normal conditions, there is continually a small 

 quantity of sugar passing from the liver into the hepatic vein, we might explain 

 the diabetes as due to the disappearance of those decompositions diminished 

 burning-up of the sugar in the blood which are constantly removing the sugar 

 from the blood. In fact, diabetic persons have been found to consume less O 

 (v. Pettenkofer and Voit), and to have an increased formation of urea. 



Sources of Glycogen. The "mother-substance" of the glycogen of 

 the liver has been variously stated to be the carbo-hydrates of the food 

 (Pavy), fats (olive oil, Salomon), glycerine (van Been, Weiss), taurin 

 and glycin (the latter splitting into glycogen and urea Heynsius and 

 Kiithe), the proteids (Cl. Bernard), and gelatin (Salomon). If it is 

 derived from the albumins, it must be formed from a non-nitrogenous 

 derivative thereof. 



Effects of Food. Eabbits whose livers have been rendered free 

 from glycogen by starvation, yield new glycogen from their livers 

 when they are fed with cane-sugar, grape-sugar, maltose, or starch. 

 Forced muscular movements soon make the liver of dogs free from 

 glycogen, and exposure to cold diminishes its amount. Dextrin and 



23 



