576 DIABETES. [BOOK n. 



know as the vaso-motor centre, or at least of a part of that 

 region. 



370. With regard to the exact nature of the influence 

 started by the puncture of the spinal bulb, and the path by which 

 that influence reaches the liver, our information is at present 

 very imperfect. One thing seems clear, viz. that the influence 

 in question is not carried down by the main vagus trunks ; for 

 not only has the section of both these nerves in the neck no 

 marked effect in the way of producing diabetes ; but the 

 ' diabetic puncture ' of the spinal bulb is as efficient after 

 division of both vagus nerves as before. The influence appears 

 to reach the lines by way of the sympathetic system ; but no 

 authoritative statement as to the exact path can as yet be made. 

 As to the nature of the influence we can perhaps at present 

 only say that most probably the normal actions of the hepatic 

 cells are in some way directly interfered with, for we have no 

 satisfactory evidence that vaso-motor changes, such as dilation 

 of the hepatic artery, and consequent increase of the supply of 

 arterial blood relatively to the supply of venous blood by the 

 portal vein, bring about the result in question. 



371. A temporary diabetes may be brought about by the 

 administration of the substance phloridzin. This however is a 

 glucoside, and part of the sugar which appears in the urine, 

 after a dose of it, may come direct from the drug itself ; but 

 the quantity of sugar discharged is too great to be accounted 

 for in this way, and similar diabetic effects are produced by the 

 administration of phloretin, a derivate of phloridzin, not a glu- 

 coside, and not giving rise to sugar by its own decomposition. 

 The sugar which appears in the urine after a dose of either of 

 these substances seems to come in part at least from the hepatic 

 store of glycogen when that is present ; but the drug will give 

 rise to sugar in the urine of starving animals, from whose livers 

 (and other tissues) glycogen is presumably absent. 



Artificial diabetes is also a prominent symptom of urari 

 poisoning. This is not due to the artificial respiration, which 

 is had recourse to in order to keep the urarized animals alive ; 

 because, though disturbance of the respiratory functions suffi- 

 cient to interfere with the hepatic circulation may produce 

 sugar in the urine, artificial respiration may with care be 

 carried on without any sugar making its appearance. More- 

 over, urari causes diabetes in frogs, although in these animals 

 respiration can be satisfactorily carried on without any pul- 

 monary respiratory movements. The exact way in which this 

 form of diabetes is brought about has not yet been clearly made 

 out. 



A very similar diabetes is seen in carbonic oxide poisoning ; 

 and is one of the results of a sufficient dose of morphia, or 

 amylnitrite and of some other drugs. 



