86 DISACCHARIDES, POLYSACCHARIDES AND GLUCOSIDES 



or for an hour with four per cent, sulphuric acid at 80 (/., we obtain 

 "Amylodextrin," which yields a port-wine coloration with iodine. 

 Further hydrolysis of the amylodextrin yields a mixture of simple 

 dextrins which give no color with iodine (" Achroodextrin") ; still further 

 hydrolysis yields Glucose, an intermediate product of hydrolysis being 

 Maltose which, however, in the acid-hydrolysis of starch, is immediately 

 broken down into glucose, so that in the hydrolysis of starch by acids 

 maltose is only transiently present in the system. In the hydrolysis 

 of starch by diastatic ferments, however, unless Maltase be also present, 

 the final product of hydrolysis is the disaccharide maltose, the inter- 

 mediate stage of hydrolysis being so far as we know, similar to those 

 observed in the hydrolysis of starch by acids. The hydrolysis of 

 starch takes place, therefore, step by step, with the production of 

 intermediate stages of hydrolysis before the final product, glucose, 

 is obtained. We shall meet with analogous phenomena among the 

 proteins, and if we draw a parallel, which is of course only justifiable in 

 a formal, not in a chemical sense, between the hydrolysis of starch and 

 the hydrolysis of proteins, then we would have the following table of 

 analogues: 



Starch analogous to Proteins 



"Soluble starch' 



Amylodextrin 



Achroodextrins 



Maltose 



Glucose 



Albumoses 



Peptones 



Polypeptids 



Dipeptids 



Amino-acids 



Inulin, a polysaccharide found in the tubers of dahlias, and in other 

 situations, bears the same relationship to fructose that starch does to 

 glucose. On hydrolysis by acids it yields only fructose; it is not 

 hydrolyzed by any of the diastatic ferments which hydrolyze starch 

 or glycogen. It is> however, hydrolyzed by a special ferment Inulinase. 

 Inulin differs very markedly from starch, in that it dissolves readily 

 in warm water with the formation of a solution instead of a paste, and 

 it yields a yellow color with iodine. 



In various other situations in the vegetable kingdom other poly- 

 saccharides resembling starch and inulin are found, differing from these, 

 however, in certain characteristics. Thus we have Amylin, Lavosin, 

 Cerosin, and Secalin, etc., found in grain-seeds, some of which yield 

 glucose on hydrolysis, others fructose. In Lupinus luteus is found 

 Galactin, a polysaccharide which yields only galactose on hydrolysis. 

 In Lichens is found a polysaccharide, Lichenin, which yields only 

 glucose on hydrolysis by acid, but which, curiously enough, is not 

 hydrolyzed by diastatic ferments. It yields a yellow color on treat- 

 ment with iodine. 



Glycogen is to the animal economy what starch is to that of the plant. 

 It was observed by the distinguished French investigator, Claude 

 Bernard, in 1848, that the sugar-content of the liver, excepting after 

 starvation, is very high. He further found that the sugar which the 



