CARBOH YDRA TES 1 83 



The conversion into maltose is effected by two ferments^ 

 Ptyalin, present in saliva, and Amylase, secreted by the 

 pancreas. The disaccharides are hydrolysed by three fer- 

 ments present in the succus entericus — maltose by Maltase, 

 lactose by Lactase, and cane sugar by Invertase (so called 

 because in the process the optical activity of the solution 

 is inverted). 



Metabolism of Carbohydrates 



The only carbohydrates which can be absorbed by the 

 intestine are the monosaccharides. Of these the most 

 important is glucose. This sugar is the ultimate hydrolytic 

 product of starch, cellulose and maltose, and it is a con- 

 stituent of the disaccharides cane sugar and lactose. The 

 glucose absorbed is practically all oxidised in the tissues 

 to carbonic acid and water, the rate of oxidation being 

 determined by the activity of the tissues. 



Glucose, then, is being added to the blood intermittently 

 from the intestine, and is beiftg destroyed at a rate varying 

 with the physiological activity of the body. Yet the 

 amount of glucose in arterial blood remains fairly constant 

 (0- 10-0- 15 per cent.). These facts indicate on the part of 

 the body a considerable capacity for carbohydrate storage, 

 and at the same time a mechanism for regulating a constant 

 currency of glucose in the blood. 



The Excretion of Sugar 



Glucose occurs in normal urine to the extent of about 

 1 part in 1000 — that is to say, in about the same concen- 

 tration as in the blood. Such an amount, however, is not 

 recognisable by the ordinary methods. When for any 

 reason there is an increase in the blood-sugar (Hyper- 

 glycsemia) glucose appears in the urine (Glycosuria), but 

 in a far higher concentration than in the blood. Assuming 

 that the kidneys are acting normally, glycosuria indicates 

 hyperglycaemia, though the amount of sugar in the urine 

 is no measure of the amount of sugar in the blood. 



