140 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



LESSON XIII 

 CABBOHYDBATES 



1. Glycogen. — A rabbit which has been fed five or six hours previously 

 on carrots is killed by bleeding. The chest and abdomen are opened quickly 

 and a cannula inserted into the portal vein, and another into the vena cava 

 inferior. A stream of salt solution is then allowed to pass through the liver 

 until it is vmiformly pale. The washings are collected in three beakers 

 labelled a, b, and c. 



The liver is cut out quickly, chopped into small pieces, and thrown into 

 boiling water acidulated with acetic acid. The acidulated water extracts a 



small quantity of glyco- 

 gen. The pieces of scalded 

 liver are then groimd up 

 in a mortar with hot 

 water, and thoroughly 

 extracted with boiling 

 water. Filter. A strong 

 solution of glycogen is 

 thus obtained. 



Test the solution when 

 cold with iodine. 



To separate the glyco- 

 gen^ evaporate the solu- 

 tion to a small bulk on the 

 water-bath and add excess 

 of alcohol ; the glycogen 

 is precipitated as a floccu- 

 lent powder, which is col- 

 lected on a filter and dried 

 in an oven at the tempe- 

 rature of 100° (see fig. 55). 



us regulator («). (Gscheidlen.) 



If the experiment is to be a quantitative one, the piece of liver taken and 

 the glycogen obtained must be weighed. 



' This method of preparation of glycogen has the advantage that only traces 

 of proteid are mixed with it. In KiUz's method (extraction with dilute potash) 

 there is more proteid. This is precipitated by the alternate addition of hydro- 

 chloric acid and potassio-mercurio iodide. 



