March 13, 1908] 



SCIENCE 



429 



least in part, to geographical segregation. If 

 further studies should show that there is seg- 

 regation, geographical or ecological, between 

 these forms, then they are species; if not, they 

 are varieties, which fact then also will he 

 expressed in their morphological condition, 

 one form running into the other at least in 

 certain parts of their ranges. 



A. E. Ortmann 

 Cabnegie Museum, 



PiTTSBUKG, Pa., 

 November 23, 1907 



SPECIAL ARTICLES 



CARBOHYDRATE METABOLISM 



When we consider the fact that the products 

 of the oxidation of sugars in vitro are not 

 well known, the uncertainty that prevails re- 

 garding the mechanism of utilization of the 

 common sugars in the body can be understood. 

 Not only are the products of their metabolism 

 unknown, but the form in which the carbo- 

 hydrate must reach the cell to be available as 

 a food is also not beyond dispute. It is ordi- 

 narily held that the cell can utilize sugar as 

 such. On the other hand, some hold that the 

 sugar must reach the cell in a colloid form or 

 combination to act as a food. Again, it is 

 claimed that dextrose is the form in which 

 sugar is utilized by the tissues, and that the 

 other sugars, as levulose or galactose, are 

 transformed into dextrose before they are oxi- 

 dized. The present preliminary report aims to 

 give the results of some work on this problem. 



The method adopted consists essentially of 

 perfusing an organ with blood containing a 

 known quantity of the sugar under investiga- 

 tion, and determining the loss after perfusion. 

 The weight of the organs before and after 

 perfusion is taken into account; the loss in 

 volume of the perfused liquid; the gain in 

 weight of the organ and the total carbohydrate 

 before and after perfusion. In this way the 

 quantity utilized by the organ may be de- 

 termined. Perfusion was also done in dead 

 organs to see that the mechanical construction 

 had nothing to do with the loss of sugar. 

 Also samples of the liquid were kept at the 

 temperature of the perfused blood (37-40° C.) 

 during the time of perfusion to ascertain the 



extent of glycolysis occurring without per- 

 fusion. 



A very brief summary of results will be 

 given : 



Experiment I. — Perfusion of the hind legs 

 of a dog with dextrose-blood solution. The 

 legs were stimulated at 30 times per minute 

 and the perfusion was made at the rate of 

 about 125 c.e. in ten minutes. 



Dextrose 

 per mille. 



Blood before perfusion 3.1916 



Blood after 20 minutes 2.9659 



Blood after 30 minutes 2.7750 



Blood after 45 minutes 2.4736 



Blood after 65 minutes 1.9473 



Blood after 71 minutes 1.5384 



It is readily seen that a loss of sugar has 

 taken place. This loss could occur in one of 

 several ways: (1) by actual oxidation; (2) 

 by accumulation in the surrounding tissues; 

 (3) by storage in the tissues as glycogen, etc. ; 

 or (4) by absorption by the tissues. As a 

 result of a number of experiments it has been 

 found that beth oxidation and accumulation 

 take place. In every instance there was a 

 distinct loss of dextrose when perfused 

 through the living tissue. The accumulation 

 by edema and other means increased as the 

 tissues died, and in the dead organs an ac- 

 cumulation took place without any oxidation. 



When the liver was perfused, there was 

 likewise a loss of sugar. No glycogen storage 

 occurred unless the perfusion was commenced 

 very rapidly after the interruption of the 

 circulation. In other words, the glycogen- 

 storing function of the liver was lost much 

 more quickly than the glycolytic function. 

 No definite conclusions could be drawn as to 

 the influence of the hepatic circulation when 

 perfusion was made through the hepatic 

 artery, simultaneously with the perfusion 

 through the portal, the ordinary method used. 



The utilization of levulose: What has been 

 said of dextrose will hold good for levulose. 

 A brief summary of results with this sugar 

 will illustrate. 



Weight of perfused leg 1,000 gms. 



Weight of muscles of same 610 " 



Weight of opposite leg 1,020 " 



