Dr. Mitchell on the Occurrence of Sugar in the Animal Economy. 89 



3. The lymph ft-om the thoracic duct appeared to contain not a trace 

 of sugar. 



These two last experiments were performed by M. Bernard about 

 twelve months ago, and were repeated by him several times with inva- 

 riably the same results. I have also myself, for further accuracy, per- 

 formed the experiments under circumstances slightly varied, in order to 

 avoid as far as possible the occurrence of any error. They come, there- 

 fore, to be of a nature deserving the greatest confidence. They do not 

 certainly point out definitely the origin of sugar in the blood of animals, 

 fed on azotised food or fasting, which was the question for the solution of 

 which the experiments were instituted, but they draw forcibly our atten- 

 tion to the unaccountable fact, that the vena porta seems to contain in its 

 blood a very large amount of sugar, whilst the contents of the intestine in 

 both cases contained not a trace. 



I may here state, for the information of the non-professional gentlemen 

 present, that the portal vein is that which returns the blood from all the 

 chylopoietic viscera, or organs concerned in the formation of the chyle, to 

 be distributed through the liver. It is formed principally by the con- 

 fluence of the splenic and mesenteric veins, receiving contributions also 

 from the pancreas, duodenum, stomach, and gall bladder. The portal 

 vein is thus made up principally of the veins returning from the intestines, 

 spleen, and pancreas. It seemed, therefore, very singular that the blood 

 of this vein should contain such large quantities of sugar, while the con- 

 tents of the stomach and intestine were entirely devoid of it. The follow- 

 ing experiments were naturally suggested, as likely to throw light on this 

 difliculty. 



1st Exjyeriment.—HsLYiag killed as quickly as possible, that is in some 

 seconds, by division of the spinal bulb, a dog in digestion of matters 

 exempt from sugar or starch, the abdomen was immediately opened, and 

 then, with the greatest possible quickness, ligatures were placed on the 

 following vessels, viz. : — 1st, Veinous branches from the small intestine, 

 and not far from the intestine ; 2d, On the splenic vein ; 3d, On the pan- 

 creatic veinous branches ; 4th, On the trunk of the vena porta. Then 

 opening these vessels between the ligature and the organ, blood was col- 

 lected from these different sources : the small intestine, the spleen, the 

 pancreas, and that which flowed backwards from the liver. 1st, In the 

 blood from the intestinal veins, the existence of sugar was rendered 

 evident. 2d, The blood from the spleen gave no indication of its pre- 

 sence, nor did that (-^d,) from the pancreatic branches. 4th, In the 

 blood which flowed from the vena porta, very freely, when divided, as in 

 the other cases, between the organ and the ligature, large quantities of 

 sugar were found to exist. On seeing then the blood from the liver con- 

 taining so much sugar, it was presumable that some would also exist in 

 its tissue. A portion of the liver of this dog was therefore analysed, and 

 sugar detected in gi-cat abundance ; while the tissues of the spleen and 



