8 Feb., 1907.] 



Elements of Animal Physiology. 



85 



name. The malt extract of commerce is chiefly composed of a maltose 

 syrup. Maltose is a most important sugar from a bio-chemical stand-point, 

 for into it all the starch of food must be changed by the action of digestive 

 ferments before absorption by the bowel can take place. Maltose can be 

 prepared in quantity by allowing seeds rich in starch to germinate or by 

 subjecting starch itself to the action of the ferment diastase. Maltose, as 

 is well known, ferments readilv with veast ; it also gives the copper 

 sulphate reaction. 



STARCH GRAINS (AFTER VOGl). 



(a) Bean, {b) Pea. {c) Lentil, (d) Potato. 



3. Lactose, called also milk sugar. This disaccharide, when boiled 

 with an acid, splits into a mixture of dextrose and galactose. It gives the 

 copper sulphate test, but ferments very slowly or not at all with ordinary 

 yeast. It is not so sweet to the taste as the other disaccharides and' is not 

 so soluble. It is of importance in that it is the carbohydrate ingredient of 

 milk, and is not produced anywhere in the animal kingdom except in the 

 mammary gland (udder) of a mammal. It is readily attacked in solution 

 by a bacillus {hacillus lactis) and transformed into lactic acid, a change 

 which accounts for the souring of milk. 



TRISACCHARIDES. — Only one trisaccharide is of importance, 

 namely, raffinose, which is present in cotton seed, eucalyptus manna, and. 



