ANIMALS AND PLANTS. 169 



of working up mere mineral matters into complex or- 

 ganic compounds. 



Contrariwise, there is a no less wide foundation 

 for the generalisation that animals, as Cuvier puts it, 

 depend directly or indirectly upon plants for the ma- 

 terials of their bodies; that is, either they are her- 

 bivorous, or they eat other animals which are herbi- 

 vorous. 



Bat for what constituents of their bodies are ani- 

 mals thus dependent upon plants? Certainly not for 

 their horny matter; nor -for chondrin, the proximate 

 chemical element of cartilage ; nor for gelatine ; nor for 

 syntonin, the constituent of muscle ; nor for their ner- 

 vous or biliary substances ; nor for their amyloid matters ; 

 nor, necessarily, for their fats. 



It can be experimentally demonstrated that animals 

 can make these for themselves. But that which they 

 cannot make, but must, in all known cases, obtain di- 

 rectly or indirectly from plants, is the peculiar nitro- 

 genous matter, protein. Thus the plant is the ideal 

 proletaire of the living world, the worker who pro- 

 duces; the animal, the ideal aristocrat, who mostly oc- 

 cupies himself in consuming, after the manner of that 

 noble representative of the line of Zahdarm, whose epi- 

 taph is written in Sartor Eesartus. 



Here is our last hope of finding a sharp line of de- 

 marcation between plants and animals; for, as I have 

 already hinted, there is a border territory between the 

 two kingdoms, a sort of no-man's-land, the inhabitants 



