METABOLISM. 65 



separation of its carbon from the combined oxygen so that 

 it may enter into one or other form of carbo-hydrate, is not 

 now ordinarily effected, as we must assume it once was, by 

 the undifferentiated protoplasm; but is effected by a 

 specialized substance, chlorophyll, imbedded in the proto- 

 plasm and operating by its instrumentality. The chloro- 

 phyll-grain is not simply immersed in protoplasm but is 

 permeated throughout its substance by a protoplasmic net- 

 work or sponge-work apparently continuous with the proto- 

 plasm around ; or, according to Sachs, consists of protoplasm 

 holding chlorophyll-particles in suspension: the mechanical 

 arrangement facilitating the chemical function. The result- 

 ing abstraction of carbon from carbon-dioxide, by the aid of 

 certain ethereal undulations, appears to be the first step in 

 the building up of organic compounds the first step in the 

 primary anabolic process. We are not here concerned with 

 details. Two subsequent sets of changes only need here to 

 be noted the genesis of the passive materials out of which 

 plant-structure is built up, and the genesis of the active mate- 

 rials by which these are produced and the building up effected. 

 The hydrated carbon which protoplasm, having the chloro- 

 phyll-grain as its implement, produces from carbonic acid 

 and water, appears not to be of one kind only. The possible 

 carbo-hydrates are almost infinite in number. Multitudes of 

 them have been artificially made, and numerous kinds are 

 made naturally by plants. Though perhaps the first step in 

 the reduction of the carbon from its dioxide may be always 

 the same, yet it is held probable that in different types of 

 plants different types of carbo-hydrates forthwith arise, and 

 give differential characters to the compounds subsequently 

 formed by such types : sundry of the changes being katabolic 

 rather than anabolic. Of leading members in the group 

 may be named dextrin, starch, and the various sugars 

 characteristic of various plants, as well as the cellulose 

 elaborated by further anabolism. Considered as the kind of 

 carbo-hydrate in which the products of activity are first stored 



