CARBOHYDRATES. 77 



and its transformation into glucose, both changes being functions of the 

 liver cells, partly directly and partly indirectly, were dependent upon 

 the nervous system. He showed this by means of the following classical 

 experiment, which was first performed upon rabbits. If a rabbit is injured 

 at a certain place in the medulla, sugar appears in the urine after a 

 short time. This region is bounded above by the origin of the two audi- 

 tory nerves, and below by a line connecting the places of origin of the 

 vagus nerves. The experiment is carried out in this way: After tying 

 the rabbit, the point of a trocar is placed in the median line upon the 

 os occipitale exactly at the Protuberantia occipitalis superior, and then 

 pushed through carefully until the Pars basillaris is reached. The instru- 

 ment thus bores through the skull, the cerebellum, and the posterior 

 and median columns of the medulla. Two hours after the operation 

 sugar appears in the urine. The elimination of sugar, however, in such 

 cases is not lasting, usually disappearing at the end of five or six hours. 

 With dogs, however, this glucosuria lasts longer. Claude Bernard in one 

 case found it to last for a week. In such cases the amount of sugar con- 

 tained in the urine is not large, usually amounting to merely two or three 

 per cent. 1 Bernard shows the cause of the sugar elimination to be an 

 excessive amount of blood-sugar. He found, instead of the customary 

 0.1 to 0.15 per cent, more than 0.3 per cent. This operation also has the 

 same result when performed with birds 2 or with frogs. 3 



An observation made by F. W. Dock 4 is of considerable importance for 

 complete understanding of this kind of glucosuria. He found that the 

 above operation succeeded only with well-nourished animals, i.e., with those 

 which possessed stored-up glycogen. Naunyn 5 arrived at the same con- 

 clusion. He showed that the success of the so-called " diabetic puncture " 

 depended wholly upon the state of nourishment of the animal experimented 

 upon. Dissection of the animal after the operation always showed that the 

 liver was free from glycogen. The fact that the liver in this case loses the 

 power of storing up sugar in the form of glycogen is shown by the following 

 experiment: If a solution of d-glucose is injected into the mesenteric 

 vein of a dog whose liver has been deprived as far as possible of glyco- 

 gen by starvation, only very small amounts of sugar will subsequently 

 be found in the urine. If the same experiment is repeated with another 

 animal which has undergone the " diabetic puncture," a marked glucosuria 

 ensues soon after the injection of the sugar. 6 



1 H6don: Diabete, Dictionnaire de Physiol. 4, 812. 



2 M. Bernhardt: Virchow's Arch. 59, 407 (1874). 



8 M. Schiff: Untersuchungen iiber die Zuckerbildung, Wiirzburg, 1859. 



4 Pfliiger's Archiv. 5, 571 (1872). 



6 Arch, exper. Path. Pharm. 3, 85 (1875). 



Cf. P. Levine: Zentr. Physiol. 8, 397 (1894). 



