448 THE CAT. [chap. xiii. 



Now, all plants, except tlie very lowest, have their constituent 



, protoplasm divided into a number of minute separated parts (or 



cells), each such separated part being enclosed within an 



envelope of cellulose. But in no animal whatever does this 



obtain. 



There are, however, lowly animals and plants which consist 

 each of a single particle of protoplasm, but almost all unicellular 

 plants are enclosed within a cellulose envelope — an investment 

 which is wanting in such lowly animals. In regard to structure 

 then, we have thus an almost complete distinction between all 

 animals and almost every single plant. 

 B. As regards function, there is a still more important distinction. 

 The cat's body is, as we have seen, reducible to a certain 

 number of chemical elements. Let a living cat be supplied 

 with these same elements, in whatsoever combinations artificially 

 produced, and in the greatest abundance, and the animal will 

 none the less starve to death, however much it may eat of such 

 substances. For the cat possesses no power of building up its 

 tissues from inorganic matter, but absolutely needs for its sub- 

 sistence a food consisting of organic matter already formed. It 

 may be said that such is the case because the cat is a beast of 

 prey. But it is the very same thing with the mice, young 

 rabbits, or grain-eating birds, on which the cat may live. 

 None of these vegetable-feeding creatures can, any more than 

 the cat, live upon the inorganic world exclusively. Nor can 

 other animals, however lowly, do so, for though a few worms 

 have an exceptional power in this respect, yet even they also 

 feed, like other animals, upon organic matter. Thus it maybe 

 affirmed that the cat agrees with every other animal in not being 

 able to sustain itself by forming living matter (or protoplasm) 

 from the inorganic world alone. With most plants it is far 

 otherwise, they can live upon inorganic matter only, and have 

 the power of dissolving the carbonic acid of -the atmosphere, 

 and retaining its carbon while letting its oxygen go free. 

 It is by the exercise of this power that all the wood which exists, 

 and all coal (which once existed as vegetable substance) have been 

 produced. Still, not all plants possess this power ; for the group of 

 fungi, together with such parasitic plants as are devoid of green 

 foliage leaves, require, as animals do, organic matter for their food, 

 and have not the power of thus fixing carbon. 



The cat then, inasmuch as it is an animal at all, differs from 

 almost all plants : — 



(1.) In that it needs organic matter for its food, and 

 (2.) In that the protoplasm of its body is not enclosed or parti- 

 tioned by a structure of cellulose. 

 But in that it is not an animal of a lowly kind, it further differs 

 from almost all plants : — 



(1.) In its power of locomotion ; 

 (2.) Its sensitivity ; 



