644 DIABETES 



jn<i" the existence in blood of a combined sutr'ar capable of spontaneous 

 conversion into free suoar. Michaelis and Rona dialyzed separate por- 

 tions of the same blood against isotonic salt solutions containing 

 graduated quantities of sugar. A sugar solution which neither lost 

 nor gained sugar during the dialysis they regarded as having an 

 amount of free sugar e((ual to that in the blood. Titration of the 

 blood sugar and of the sugar in such a solution gave almost identical 

 figures. They accordingly concluded that all of the reducing sugar 

 in this blood must have been as free to diffuse as was that in the simple 

 salt solution. But this ingenious experiment of ^lichaelis and Rona 

 does not show conclusively that in circulating blood there is no sugar 

 in a state of colloidal adsorption, because drawn blood rapidly under- 

 goes survival changes (e.g., lactic acid formation) which might influ- 

 ence the affinity of its colloids for sugar. However, McGuigan and 

 Hess ^^ led the blood of living animals thi-ough collodion tu])es en- 

 closed in jackets filled with isotonic salt solutions and found that when 

 equilibrium was established the concentration of reducing sugar in 

 the salt solution and in the plasma was the same, proving that even 

 in life all of the titrable plasma sugar is in a state of subdivision which 

 lets it migrate through the interstices of a collodion membrane. This 

 would make the adsorption idea seem untenable. 



Closely related to the question of the state of the sugar in the blood 

 is that of its state in the cells. Palmer ^- has studied the percentages 

 of sugar found in the various tissues in relationship to the plasma 

 sugar concentration. The titrable sugar of the tissues was found 

 below that of the blood in all organs except the liver. Of course, 

 owing to the large quantities of glycogen which occur in that organ 

 and the rapidity with which it breaks down into glucose, liver tissue 

 would naturally analyze high for sugar. In the muscles the titrable 

 sugar was found at 0.04 and 0.041 per cent, with blood sugar at 0.10 

 and 0.105 per cent. On the other hand the tissues generally when 

 boiled with dilute acid show a higher content of "combined" sugar 

 than the blood. Tliis is most striking in the case of the liver and 

 due by common consent to the polymers of glucose in that organ. 



It serves a useful purpose to consider the body as a whole as an 

 heterogeneous system made up of phases, and to assume that glucose 

 on entering the body distributes itself between these phases as acetic 

 acid may distribute itself between the fat droplets and the acpieous 

 part of milk ; that glucose in a certain type of phase behaves as though 

 in water and in anothei- type of phase rapidly undergoes chemical 

 changes. The blood is a tissue in which the dominant phase is in the 

 iialui-e of a ])hysical solvent foi" glucose, like water. In the cells the 

 dominant phases are of sucli a character that glucose on entering Ihcm 



11 Jour. Pliarin. and Exp. Tlior., (1014) (G), 45. 



12 Jour. Biol, (hem., 1917 (30), 79. 



