452 A MANUAL OF PHYSIOLOGY 



kidneys will be large. If, on the other hand, the animal has 

 been starved before the operation, so that the liver is free 

 or almost free from glycogen, the puncture will cause little 

 or no sugar to appear in the urine. That nervous influences 

 are in some way involved is shown by the absence of 

 diabetes if the splanchnic nerves, or the spinal cord above 

 the third or fourth dorsal vertebra, be cut before the 

 puncture is made. But sometimes these operations are 

 themselves followed by temporary diabetes. Section of the 

 vagi has no effect either in causing glycosuria of itself or in 

 preventing the * puncture' diabetes, although stimulation of 

 the central ends of these and of other afferent nerves may 

 cause sugar to appear in the urine. Although several of the 

 operations which lead to this temporary glycosuria un- 

 doubtedly bring about changes in the hepatic circulation, it 

 is as yet impossible to say whether the whole phenomenon 

 is at bottom a vaso-motor effect, or is due to direct nervous 

 stimulation of the liver-cells, or to withdrawal of such stim- 

 ulation or control. 



The pancreas is intimately concerned in the metabolism 

 of sugar. Excision of this organ in dogs causes permanent 

 diabetes (v. Mering and Minkowski), which is prevented if a 

 portion of the pancreas be left, or if it be transplanted under 

 the skin of the abdomen (p. 483). 



Curara, morphia, carbon monoxide, phloridzin (p. 527), and 

 other substances, also cause diabetes. Phloridzin diabetes 

 agrees with pancreatic, differs from ' puncture ' diabetes in 

 this, that it can be produced in an animal free from glycogen, 

 and is accompanied by extensive destruction of proteids. It 

 differs from other forms of diabetes in being associated, not 

 with an increase, but with a diminution in the sugar of 

 the blood. This is best explained by supposing that the 

 phloridzin acts on the kidney in such a way as to increase the 

 permeability of the glomerular epithelium for sugar, or (in 

 terms of the vital theory of urinary secretion), to increase its 

 sensitiveness to the stimulus of sugar circulating in the blood. 

 The sugar is, therefore, rapidly swept out of the circulation, 

 and this leads secondarily to an increased production of 

 sugar to make good the loss. 



