9 2 4 METABOLISM. 



himself, that when the blood from the hepatic vein is collected under 

 conditions of anaesthesia, the difference between the percentage amount of 

 sugar in the hepatic blood and that in ordinary arterial blood becomes 

 greatly diminished, if it does not altogether disappear. 1 



Bernard's views have been combated strenuously by Pavy, 2 whose 

 method of experimentation is not open to the same objection as that 

 of Seegeii and others who have found a constant excess of sugar in 

 the hepatic blood. Pavy takes blood from the animal immediately 

 after it has been killed by a blow upon the head, and before there 

 has been time for any change to have occurred in the liver, and he 

 finds that blood which is collected *mder these circumstances from 

 the inferior vena cava (including, therefore, the blood which has passed 

 out from the liver) never shows any appreciable excess of reducing 

 substances over blood obtained from other parts of the body. Eesults 

 similar to those of Pavy have also been obtained, although under 

 somewhat different conditions, by other observers. 



We are therefore landed in this difficulty, as the result of the 

 imperfection of our present methods, that we cannot be sure whether 

 the blood of the hepatic vein does or does not, normally, contain an 

 excess of sugar. If it does, we are bound to assume that sugar is 

 being continually passed off from the liver into the general blood of the 

 body, and since this sugar does not pass off by the urine, it can only be 

 available for the nutrition of the tissues, and the production of energy 

 by oxidation. If sugar does not pass from the liver into the blood, we 

 should require to find some form in which the glycogen, which is 

 undoubtedly stored up in the liver, is got rid of, and also to find some 

 meaning for its presence there and in the muscles. 



It has been suggested by Pavy 3 that such stored glycogen may 

 become converted into fat. There is no doubt that carbohydrate 

 food does become converted in the body into fat, and there are 

 many instances of the formation of fat from carbohydrate material in 

 plants; it is therefore not altogether wanting in probability, that the 

 glycogen which is stored up in the liver cells and muscles may also 

 become converted into fat. Such fat may be assumed to be gradually 

 removed by the blood and carried to the different organs, and in them 

 ultimately oxidised to carbonic acid and water. 



Another supposition, which we have already considered, is that it 

 becomes directly oxidised, and produces heat. As most of the 

 oxidation of the body occurs in the muscles, and as the muscles retain 

 their glycogen in starvation longer than the liver, although the latter 

 organ contains normally a much larger proportion, it seems very 

 probable that the glycogen passes from the liver to the muscles. This 

 cannot be as glycogen, for glycogen is not present in blood plasma, and 



1 Centralbl.f. PhysioL, Leipzig u. Wien, 1896-97, Bd. x. S. 497, 822. 



2 "The Physiology of the Carbohydrates," London, 1894. Here other papers by the 

 same author are referred to. 



3 Ibid., pp. 245 to 252. In connection with the question of sugar production by the 

 liver, it may be mentioned that removal of this organ or cutting off its blood supply in 

 rabbits (Boik and Hoffmann, "Exper. Studien u. Diabetes," Berlin, 1874), dogs (Seegen. 

 "Die Zuckerbildung," and Tanyl and v. Harley, Arch. f. d. ges. PhysioL, Bonn, 1895, 

 Bd. Ixi. S. 551), geese (Minkowski, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1882, 

 Bd. xx. S. 41), is followed by either disappearance or marked diminution of the sugar of the 

 blood. 



