88 THE CHEMISTRY OF CATTLE FEEDING 



occur ; and the change, therefore, takes place " spontaneously " 

 when the substances are macerated with water. 



It is evident from the reactions which define the class that 

 the glucosides are to be regarded as esters of glucose or other 

 sugars, and as several of the simpler compounds have been 

 prepared synthetically, there is no room for doubt that this 

 view is exact. Several members of the group contain nitrogen, 

 but the majority are composed of carbon, hydrogen, and 

 oxygen only. As many glucosides are met with in other con- 

 nections, it will be sufficient for the present to mention one 

 or two typical examples. 



Amygdalin, C2oH27O 1:l N, occurs in bitter almonds, the 

 leaves of the cherry laurel, and in various parts of other plants, 

 but especially in kernels, e.g. of apricots, peaches, cherries. It 

 is soluble in water and in hot alcohol, and crystallises from the 

 latter on cooling. When bitter almonds are macerated with 

 water, the amygdalin dissolves, and the enzyme, called emulsin, 

 which is also present, effects the hydrolysis of the compound. 

 A similar change can also be brought about by the action of 

 dilute acids. The products are the same in both cases, viz. 

 glucose, hydrocyanic acid, and benzaldehyde (oil of bitter 

 almonds). 



C2oH 27 OiiN + 2 H 2 -> 2C 6 H 12 6 + C 6 H 5 CHO + HCN 



(Amygdalin.) (Glucose ) (Benzaldehyde.) 



The probable constitution of the compound, therefore, is 

 indicated by the formula 



C 6 H 5 .CH< Q . Ci2 H 2i0lo 



The bihexose compound is resolved into glucose when it is 

 split off. Alkalis produce a similar effect, but, of course, the 

 nitrogen is evolved as ammonia. 



Salicin, C 13 H 18 O 7 , occurs chiefly in the leaves and young 

 bark of willows, but is found also in certain species of poplar 

 and other plants. It is extracted with boiling water and can 

 be easily crystallised. It has an extremely bitter taste, but is 

 quite neutral to litmus. By the action of ferments or of dilute 



