152 THE CARBOHYDRATES 



On the other hand, Meyer * was of opinion that starch 

 granules consisted essentially of two substances known respec- 

 tively as a- and j3-amylose. The former, which was insoluble, 

 he regarded as an anhydride which could be converted into the 

 soluble P variety by the action of superheated steam. 



He also thought that when starch is acted upon by hydro- 

 chloric acid it is converted into amylo-dextrin, and considered 

 that amylo-cellulose, which Nageli regarded as an original 

 constituent of the starch granule, was in reality identical with 

 amylo-dextrin, and therefore a secondary product of the action 

 of acid on the amylose. 



It is to the French workers Maquenne and Roux,t and 

 Fernbach and Wolff $ that we owe the first definite ideas 

 concerning the existence of two distinct substances. They 

 stated that starch granules consist of two substances, amylo- 

 cellulose or amylose. and amylopectin ; the term amylocellu- 

 lose was not equivalent to Nageli's starch cellulose but to his 

 granulose ; we thus get the following equivalents : — 



Nageli. Meyer. Maquenne and Roux. 



Outer layer or starch a- Amylose. Amylopectin. 



cellulose. 



Inner layer or granulose. /3-Amylose. Amylocellulose or amylose. 



Maquenne first stated that amylose formed 80 per cent 

 and amylopectin 20 per cent by weight of the starch granule ; 

 the former substance was described as being soluble in water 

 and giving a blue colour with iodine, while the latter would 

 only swell in water without dissolving, and was erroneously 

 stated to give no colour with iodine. 



The isolation of amylopectin was first effected by Gatin 

 Gruzewska,§ who treated starch with i per cent caustic soda 

 whereby the granules burst and the amylose constituent 

 entered into solution leaving the swollen outer shells of amylo- 

 pectin ; on neutralizing with acetic acid, the amylopectin 

 shrivels and can be filtered off and washed and dried. Ling 



* Meyer : " Unters. ii. d. Starkekorner," Jena, 1895. 



t Maquenne and Roux : " Compt. rend.," 1903. 137, 88 ; 1905, 140, 



1303- 



I Fernbach and Wolff : id., 1904, 138, 819. 



§ Gatin Gruzewska : " Compt. rend. Soc. biol.," 1908, 64, 178. 



