90 Dr. JIitchell on the Occurrence of Sugar in the Animal Economy. 



pancreas, treated in the same way and with equal care, gave no indica- 

 tions of its presence. 



2d Experimeiit. — I bled a rabbit, which had been kept fasting for 

 several days, from the veins which return the blood from the fore and 

 hind legs, and in the serum of neither could I detect the presence of 

 sugar. While in the blood from the right side of the heart, and in the 

 infusion of the liver of the same animal, it existed in abundance. 



od Exjjeiiment. — Another rabbit, which had also been subjected to a 

 lengthened abstinence fi'om food, was the subject of the next experiment. 

 A ligature was applied to the portal vein, through as small an aperture 

 in the abdominal cavity as possible. The vessel was then opened on both 

 sides of the ligatui'c, and the blood from each portion laid aside for coagu- 

 lation, and the same was done with a small portion from the mesenteric 

 artery (the vessel which conveys the arterial blood, or blood from the 

 heart to the intestines). In the arterial blood, and in that from the vein 

 between the ligature and the gut, no sugar could be detected, or if any, 

 a mere trace. Nor did any proof appear of its presence in the matters 

 contained in the stomach and small intestine. But in the blood from the 

 portal vein, between the ligature and the liver, as well as in infusions of 

 the tissue of the liver, I found sugar in very considerable abundance. 



From all this it appears that the liver is in some way the source whence 

 the sugar comes, in such cases at least as those wherein the animal has 

 been confined to a nitrogenised diet, or which amounts to the vei*y same 

 thing, subjected to long fasting. 



Sugar is not found in the blood going to the intestine, nor in the hlood 

 coming from it and going to the liver, nor in the hlood coming from the 

 spleen and going to tJie liver, nor in that coming from the pancreas and 

 going to the liver, nor in the tissues of the spleen or j)cmcreas, nor in the 

 contents of the stomach and intestine, and yet is found in abundance in the 

 tissue of tlie liver. I repeat, that from all this it appears that in some 

 way or other the liver is the origin or seat of this sugar, at least in such 

 cases as those wherein the animal had been confined to a nitrogenised 

 diet, or which amounts to the very same thing, subjected to long fasting. 



Before proceeding to the examination of this result, I shall cite one 

 other experiment, briefly. Exp)eriment. — In rabbits fed on potatoes and 

 beet root, I was able to detect sugar in the blood from any part of the 

 mesenteric veins, as also indeed throughout the whole circulation. But 

 here again it appeared in greater quantity in the liver than elsewhere. 



A moment's reflection on what has been written will at once suggest 

 the query, — if the sugar is formed in the liver, how does it find its way 

 back again into the portal vein ? We never find in the general circula- 

 tion that blood, which has already passed a capillary tissue by a progres- 

 sive movement, ever retrogrades. But this reflux in the portal vein, I 

 conceive more easy of explanation than may be imagined. In a physio- 

 logical state the portal circulation is mainly dependent on the pressure 



