424 PRACTICAL PHYSIOLOGY 



are hydrolysed. On standing, also, the rotatory power may increase 

 (half rotation) or diminish (bi-rotation). 



Cane Sugar + 66,5 after hydrolysis becomes laevorotatory. 

 Maltose ; + 137 - after hydrolysis becomes less shows bi-rotation. 

 Lactose; +52,5. 



Fermentation of Sugars with Yeast. Shake up a 1 per cent, 

 solution of dextrose, which has been previously boiled to expel air, with 

 a piece of yeast the size of a split pea. Place the opalescent solution 

 thus obtained in a Southall's ureometer (p. 274) so that it completely 

 fills the vertical tube. Now place the tube in the incubator over night 

 when it will be found that a certain amount of gas (C0 2 ) has collected 

 at the top of the tube. As a control a tube should be filled with 

 water and yeast. 



Repeat this experiment with similar solutions of the various sugars, 

 and note that after 24 hours lactose and cane sugar have scarcely under- 

 gone any fermentation. If they be left longer, however, a considerable 

 amount of gas will collect since hydrolysis is gradually produced by 

 another ferment (invert ferment) in the yeast, on the products of which 

 the alcoholic ferment then acts. 



CHAPTER II. 

 GLYCOGEN. 



THE following chapter includes an accurate method for the estimation 

 of glycogen in organs or tissues, and shows how the post-mortem trans- 

 formation of glycogen into sugar may be demonstrated. A dog or a 

 rabbit is killed by an overdose of chloroform, the abdomen quickly 

 opened and a cannula placed in the portal vein. The liver is excised. 

 The carmula is connected, by means of indiarubber tubing, with a 

 pressure bottle containing iced water, which is perfused through the 

 hepatic blood-vessels till the liver becomes quite pale and the washings 

 colourless. The iced water also cools down the liver and hinders the 

 post-mortem transformation of glycogen with sugar. 



The liver is then divided into two, arid each half quickly weighed. 



One half A is placed in an incubator. (An incubator may be im- 

 provised by placing a large beaker on a water bath, the flame under 

 which is kept low so that the temperature of the beaker does not rise 

 above 36 C.) 



In the other half B the glycogen and sugar are determined. 1. For 

 the estimation of glycogen Pfliiger's method is employed. This is as 

 follows : 100 gr. liver are quickly chopped up into small pieces and 



