242 GLYCOGEN AND GLUCOSE IN THE LIVER. 



pearance of sugar in the urine. Schiff 1 has even found that in various 

 animals, by simply compressing the abdominal aorta for ten minutes, or 

 by tying the principal bloodvessels of one limb, he has induced, for the 

 time, a condition of diabetes. These diiferent causes may all operate 

 by accelerating the hepatic circulation as well as that of the abdominal 

 organs generally. 



III. A saccharine condition of the blood and urine may also be in- 

 duced by puncture of the medulla oblongata in the floor of the fourth 

 vertricle. This remarkable fact, which was first discovered by Bernard, 2 

 may be demonstrated in both carnivorous and herbivorous animals. It 

 is best shown in the rabbit by introducing a narrow chisel-shaped 

 instrument, with the cutting edge directed transversely, through the 

 back part of the skull and the cerebellum, so that it shall pierce the pos- 

 terior part of the medulla exactly in the median line, without passing 

 completely through its substance. Glucose appears in the urine after 

 from one to two hours and continues to be present for two or three days. 

 The immediate effect of this operation, according to the direct observa- 

 tions of Bernard, is to increase the activity of the abdominal and 

 hepatic circulation. It is not due to a direct influence conveyed by the 

 pneumogastric nerve, since the result follows, as usual, although the 

 pneumogastric nerves may have been divided, and neither division nor 

 irritation of these nerves produces a similar effect. When successfully 

 performed, the operation causes no serious disturbance of the vital 

 functions, and the animal recovers after a few days without suffering 

 permanent injury. 



In all the instances above mentioned, the appearance of sugar in the 

 urine is only temporary, depending upon an occasional disturbance of 

 the circulation. When in the human subject this condition becomes 

 permanent, it constitutes the disease known as Diabetes mellitus. In 

 this affection, which is generally progressive and fatal, the urine is 

 increased in quantity, of greater specific gravity than natural, and 

 continuously charged with sugar, sometimes in excessive abundance. 

 Fluctuations are observable in the quantity of glucose discharged at 

 different periods of the digestive process, but it may continue to appear, 

 even when no starchy or saccharine matter is taken with the food. 



1 Journal de 1' Anatomic et de la Physioloerie. Paris. 1866. No. iv. p. 365. 



2 LeQons de Physiologie Experimeutale. Paris, 1855, p. 290. 



