DIFFERENCES BETWEEN ANIMALS AND PLANTS. I I 



rating the proteinaceous matter or protoplasm which consti- 

 tutes the physical basis of life. Plants, therefore, take as food 

 very simple bodies, and manufacture them into much more 

 complex substances. In other words, by a process of deoxida- 

 tion or unburning, rendered possible by the influence of sun- 

 light only, plants convert the inorganic or stable elements 

 ammonia, carbonic acid, water, and certain mineral salts into 

 the organic or unstable elements of food. The whole problem 

 of nutrition may be narrowed to the question as to the modes 

 and laws by which these stable elements are raised by the vital 

 chemistry of the plant to the height of unstable compounds. 

 To this general statement, however, an exception must seem- 

 ingly be made in favour of certain fungi, which require organ- 

 ised compounds for their nourishment. 



On the other hand, no known animal possesses the power 

 of converting inorganic compounds into organic matter, but 

 all, mediately or immediately, are dependent in this respect 

 upon plants. All animals, as far as is certainly known, require 

 ready-made proteinaceous matter for the maintenance of exist- 

 ence, and this they can only obtain in the first instance from 

 plants. Animals, in fact, differ from plants in requiring as food 

 complex organic bodies which they ultimately reduce to very 

 much simpler inorganic bodies. The nutrition of animals is 

 a process of oxidation or burning, and consists essentially in 

 the conversion of the energy of the food into vital work ; this 

 conversion being effected by the passage of the food into living 

 tissue. Plants, therefore, are the great manufacturers in nature, 

 animals are the great consumers. 



Just, however, as this law does not invariably hold good for 

 plants, certain fungi being in this respect animals, so it is 

 not impossible that a limited exception to the universality of 

 the law will be found in the case of animals also. Thus, in 

 some recent investigations into the fauna of the sea at great 

 depths, a singular organism, of an extremely low type, but 

 occupying large' areas of the sea-bottom, has been discovered, 

 to which Professor Huxley has given the name of Bathybius. 

 As vegetable life is extremely scanty, or is altogether wanting, 

 in these abysses of the ocean, it has "been conjectured that 

 this organism is possibly endowed with the power otherwise 

 exclusively found in plants of elaborating organic compounds 

 out of inorganic materials, and in this way supplying food 

 for the higher animals which surround it. The water of the 

 ocean, however, at these enormous depths, is richly charged 

 with organic matter in solution, and this conjecture is thereby 

 rendered doubtful. 



