388 THE CHEMICAL COMPOSITION OF THE BODY. [CH. xxv. 



acids, or by means of inverting ferments such as that occurring 

 in the intestinal juice. It then takes up water, and is split into 

 equal parts of dextrose and levulose. 



C 12 H 22 U + H 2 = C 8 H 12 6 + C a H 10 B . 

 [Cane sugar] [Dextrose] [Levulbse] 



With yeast, cane sugar is first inverted by means of a special 

 soluble ferment secreted by the yeast cells, and then there is an 

 alcoholic fermentation of the glucoses so formed. 



Lactose, or Milk Sugar, occurs in milk. It is occasionally 

 found in the urine of women in the early days of lactation, or 

 after weaning. It is crystallisable, dextro-rotatory, much less 

 soluble in water than other sugars, and has only a slightly sweet 

 taste. It gives Trommer's test, but when the reducing power is 

 tested quantitatively by Fehling's solution it is.fouud to be a less 

 powerful reducing agent than dextrose, in the proportion of y to 10. 



When hydrolysed by similar agencies as those mentioned in 

 connection with cane sugar it takes up water and splits into 

 dextrose and galactose. 



C 12 H I2 U + H 2 = C H 12 + C 6 H ]2 8 . 

 [Lactose; t Dextrose] [Galactose] 



With yeast it is first inverted, and then alcohol is formed. This, 

 however, occurs slowly. 



The lactic acid fermentation which occurs when milk turns sour 

 is brought about by lactic acid micro-organisms, which are some- 

 what similar to yeast cells. Putrefactive bacteria in the intestine 

 bring about the same result. The two stages of the lactic acid 

 fermentation are represented in the following equations : 



(i.) C, 2 H 22 + II 2 = 4 C 3 H 6 0, 

 [Lactose] [Lactic acid] 



(2.) <iC 3 H 6 3 = 2C 4 H 8 2 + 4 C0 2 -} 4 H 2 . 

 [Lactic acid] [Butyric acid] 



Maltose is the chief end product of the action of malt diastase 

 on starch, and is also formed as an intermediate product in the 

 action of dilute sulphuric acid on the same substance. It is 

 the chief sugar formed from starch by the diastatic ferments 

 contained in the saliva and pancreatic juice. An isomeric sugar 

 called iso-maltose is also formed under the same circumstances. 

 It can be obtained in the form of acicular crystals, and is strongly 

 dextro-rotatory. It gives Trommer's test ; but its reducing power, 

 as measured by Fehling's solution, is one-third less than that of 

 dextrose. 



By prolonged boiling with water, or, more readily, by boiling 



