1904.] on Ionic- Dissociation Hypothesis and Vital Change. 541 



If invertase were present as a branch of the protoplasmic complex, 

 any hexose compatible with it would be attracted by it; and when 

 once in association with the complex, the sugar molecule might undergo 

 changes such as are contemplated in Baeyer's explanation of fermenta- 

 tion, the energy required to initiate these changes being derived from 

 exothermic changes proceeding simultaneously in some other part of 

 the complex. 



But it is possible to extend the conceptions which we owe to van't 

 Hoff and Emil Fischer still further. My son and I agree in thinking 

 that the assumption that enzyme and hydrolyte become associated will 

 make it possible to understand a variety of phenomena which have not 

 yet received any satisfactory explanation. For example, when con- 

 densed under laboratory conditions, formaldehyde gives rise to an 

 inactive mixture of d- and /-hexose ; but under natural conditions only 

 ^-fructose and c?-glucose are produced. If condensation took place in 

 immediate contact with a compatible enzyme, it is conceivable that a bias would 

 be given to the synthesis sufficient to determine change wholly in the one of the 

 two possible directions. 



It is a striking fact that yeast, which so readily ferments the 

 hydroschists of cane sugar, contains the two enzymes — invertase and 

 maltase — which are respectively compatible with the two hydroschists. 

 Assuming that: these enzymes are present as branches of the proto- 

 plasmic complex, it is easy to understand, from the point of view now 

 set forth, why yeast should be able to ferment both fructose and 

 glucose easily. 



On the other hand, the existence of contiguous maltase and invertase 

 branches in the protoplasmic complex might determine the formation 

 of glucose and fructose in contiguity ; and these might then unite — 

 thus giving rise to cane sugar. This conclusion is of special interest, 

 bearing in mind the observations of Horace Brown and Morris* 

 that cane sugar rather than maltose is a primary product of plant 

 metabolism. Both invertase and maltase are known to be present 

 in plants.f 



The formation of starch may be looked at from a somewhat similar 

 point of view. It may be supposed that glucose is produced initially 

 as an open chain compound and that the formation of the y-oxide 

 ring confers stability on the molecule ; it may well be that starch is 

 formed by condensation of a number of such merely potential glucose 



* ' Chem. Soc. Trans.,' 1893, vol. 63. p. 604. 



f I am still inclined, however, to favour the view which I expressed in 1890 

 (' Chem. Soc. Proc.,' p. 56), that maltose is the precursor of cane sugar in the plant : 

 it is difficult to avoid this conclusion in view of the fact that cane sugar is formed when 

 barley embryos are fed on maltose but not when they are fed on glucose, although 

 in the latter case the plantlet is found to contain invert sugar. — \_Note added 

 May 28, 1904.] 



