EXPERIMENTAL DIABETES 345 



As to the exact nature of the glycosuria -producing impulses 

 we know very little. They may merely be vaso-motor and 

 cause dilatation of the hepatic vessels whereby an increased 

 sugar production is induced (Bernard) ; or it may be that there 

 are in the splanchnics true secretory fibres concerned in the 

 control of the ferment or zymase production in the hepatic 

 cells. 



We have already seen that stimulation of the central ends 

 either of the vagus or cardiac depressor causes glycosuria. In 

 the case of the vagus, a rise, and in the case of the cardiac 

 depressor, a fall of abdominal blood pressure will result, that is, 

 opposite changes in blood pressure and still the same effect on 

 sugar production, which would seem to show that there may 

 be secretory fibres quite independent of those controlling blood 

 pressure. On the other hand, it is a well-established fact that 

 atropin paralyses all true secretory nerve terminations, whereas 

 it does not have any distinct influence on the glycosuria pro- 

 duced either by puncture of the fourth ventricle or by stimu- 

 lation of the central ends of sensory nerves (Dolley and 

 Macleod) 



Pfltiger ( 6 ) offers an ingenious speculation regarding the role 

 in the animal economy of the reflex control of sugar production in 

 the liver. Sugar is the most available food-stuff for muscular con- 

 traction, so that when a muscle contracts it uses up some sugar ; 

 at the same time, however, by compression of the muscle spindles 

 afferent nervous impulses are set up which are carried up to the 

 diabetic centre, and so lead to the liberation of more sugar from 

 the liver. The heart is the most active muscle in the body, and 

 consequently requires most sugar; its afferent fibres to the 

 diabetic centre carried in the vagus are therefore the most 

 active of all. 



In connection with puncture diabetes ought to be mentioned 

 certain experimental conditions such as the inhalation of carbon 

 monoxide, asphyxia, extensive hemorrhage itself, the administra- 

 tion of morphia, curare, strychnine, acids, &c., which are not 

 infrequently followed by glycosuria. What the exact cause of the 

 glycosuria in these cases may be whether it is by some irritation 

 of the so-called diabetic centre, either directly or through afferent 

 nerves, or whether it is some direct action of these substances on 

 the hepatic cells leading to a too rapid transformation of glycogen 



