162 ANIMALS AND PLANTS. [LECT. 



for the generalisation that animals, as Cuvier puts it, 

 depend directly or indirectly upon plants for the 

 materials of -their bodies ; that is, either they are 

 herbivorous, or they eat other animals which are 

 herbivorous. 



But for what constituents of their bodies are 

 animals thus dependent upon plants ? Certainly not 

 for their horny matter ; nor for chondrin, the proxi- 

 mate chemical element of cartilage ; nor for gelatine ; 

 nor for syntonin, the constituent of. muscle; nor for 

 their nervous 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 directly or indirectly from plants, is the 

 peculiar nitrogenous matter, protein. Thus the plant 

 is the ideal proUtaire of the living world, the worker 

 who produces ; the animal, the ideal aristocrat, who 

 mostly occupies himself in consuming, after the manner 

 of that noble representative of the line of Zahdarm, 

 whose epitaph is written in Sartor Resartus. 



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 

 of which certainly cannot be discriminated and brought 

 to their proper allegiance in any other way. 



Some months ago, Professor Tyndall asked me to 

 examine a drop of infusion of hay, placed under an 

 excellent and powerful microscope, and to tell him 



