De. Mitchell on the Occurrence of Sugar in the Anmal Economij. 91 



exercised on the viscera by the abdominal wall. When the abdomen is 

 opened, this pressure ceases by the escape of the various organs, while at 

 the same time the vessels are dragged out and elongated, and a sort of 

 depletion through the whole length of the vena porta takes place. This 

 vacuum, so to speak, aspires the blood from the liver and other organs, 

 which takes place the more readily that there arc no valves to impede 

 the retrogression of the blood. I account, therefore, in this manner for 

 the appearance of the sugar in the portal vein, and I do so the more 

 readily, that Bernard asserts that he has avoided this reflux by the 

 application of a ligature to the vein at its entrance into the liver, before 

 laying open the abdomen. 



I considei', therefore, this fact as established, that the sugar in the 

 animal economy is found concentrated in the liver. Whether it exists 

 there from some transformation of the elements of the blood taking place 

 within the organ, I cannot say, but such seems very probable. It may 

 be asserted, however, that it is merely deposited and accumulated in the 

 liver, being originally derived from some feculent or saccharine diet. 

 And this opinion is strengthened by the property which the liver i^lcnoion 

 to possess, of retaining in this manner arsenic and other metallic poisons. 

 Indeed, it cannot be denied that the liver does freqcntly play the part of 

 a condensing or accumulating organ, but in the case in rpestion experi- 

 ment shows it not to have this property. 



Expcrimeril. — A dog was subjected to abstinence both from liquid 

 and solid aliment for eight days, after this time he was supported exclu- 

 sively and abundantly on cooked flesh, principally boiled sheep's head. 

 On the nineteenth day of his sequestration, the animal was killed while 

 in full digestion. On examination his blood and liver were found to con- 

 tain sugar as abundantly as in the former experiments. 



This was also performed by M. Bernard three times under similar 

 circumstances, and with similar results. 



It cannot be imagined that this sugar had been retained during all 

 this time in the liver, for certainly the elimination must have been wholly 

 cfiected long ere the expiry of the nineteen days. One or two experi- 

 ments, afterwards to be noted, in reference to the influence of nervous 

 action on these phenomena, will serve to remove any remaining doubt on 

 this subject. 



In the discussion of a subject of such importance, it is necessary that 

 every guarantee for the accuracy of the results be given, and I shall 

 therefore now proceed to detail the methods of detecting sugar, which I 

 have employed during these and other investigations. I do not mean to 

 call the attention of the Society to all the tests which have been proposed 

 for sugar, but briefly to enumerate those on which I have placed reliance. 



Tests for Sugar. — In searching for sugar in the blood, Trommor's test 

 is that whicli is most convenient and most sure. Tlicre are various ways 



