SUGAR. 279 



consequence of the importance of the case, that I obtained from 

 one of the horses 69'4, from another 53*3, and from the third 77*2 

 grammes of portal blood, and that I employed at least two-thirds 

 of it for the determination of the sugar. The following was the 

 method of proceeding : the blood after being neutralized with 

 dilute acid and treated with four times its quantity of water, was 

 coagulated by heat, the expressed and filtered fluid was evaporated, 

 the residue extracted with spirit of 85-J-, and the spirituous fluid pre- 

 cipitated by an alcoholic solution of potash. The portion insoluble 

 in water was mixed with a little water, filtered, treated with dilute 

 sulphuric acid, for the purpose of effecting the metamorphosis 

 of any dextrin that might be present, and then examined for 

 sugar. 



We feel inclined to regard as incapable of proof these singular 

 facts (it being in direct opposition to the previously received belief, 

 that the sugar passes with facility into the blood of the intestinal 

 veins), and either to doubt the accuracy of the chemical analysis, 

 or to get over the difficulty by assuming that there is an extremely 

 rapid decomposition of the sugar in the blood. With regard to the 

 first objection which might be, and actually has been, brought 

 against this experiment, scarcely a larger quantity of blood is 

 necessary for the quantitative determination of sugar in the normal 

 fluid than was employed for this purpose in the above experiments ; 

 but there must in every case be more sugar in the blood of the 

 portal than in that of any other vein, and its existence there could 

 not be altogether overlooked. If we should further assume that 

 the sugar absorbed by the intestinal capillaries is rapidly decom- 

 posed before it can reach the trunks of the portal vein, we must 

 produce evidence that the decomposition of sugar proceeds far 

 more rapidly in the blood of the intestinal veins than in any other 

 blood. We have already seen in another place, that glucose, like 

 all other kinds of sugar, when it is injected into a vein, very soon 

 reappears unchanged in the urine ; even when very small quanti- 

 ties of glucose are injected, it admits of easy recognition in that 

 fluid. Since it has been maintained that portal blood is rich in 

 alkaline carbonates, we might be led to believe that it was the pre- 

 sence of the alkali which caused a more rapid decomposition of the 

 sugar in the portal than in any other blood. This abundance of 

 alkalies in the portal blood might probably give some support to 

 this view, if it did not happen to be a mere incidental circumstance, 

 that is to say, if it were constantly present in portal blood without 

 reference to the nature of the food which the animal had previously 



