26 ANIMAL CHEMISTRY LECTURE II. 



number of atoms contained in the molecule of salicin, as shown 

 in this table. 



x Saligenin . . C 7 H 8 O a 

 i Glucose C 6 HT,0 6 



i Salicin . . < 



i Water . . H a 



C I3 H ao 8 



Hence the necessity for the atom of water, which has to be 

 incorporated by the salicin before it can split up into its consti- 

 tuents. We may say, then, that salicin does not contain either 

 saligenin or glucose as such, but that it contains, in a state of 

 combination, a residue of saligenin and a residue of glucose, 

 which are, as it were, ever on the alert to take up water, and so 

 produce the separate and distinct molecules, saligenin and glucose 

 respectively. If we attempted to represent the composition of 

 salicin graphically, we should not place two complete circles in 

 apposition side by side, thus, 



Saligenin Glucose 



OO 



but we should place two incomplete circles, or the residues of two 

 circles, in conjunction, thus : 



Salicin 



CD 



(25.) Similarly, with regard to populin, it does not actually 

 contain saligenin, glucose, and benzoic acid, but is made up of 

 the residues of these three bodies, which can only be obtained 

 in their complete and separate state by an incorporation of the 

 elements of water with the populin, thus : 



