FUNCTIONS OF ANIMALS. 13 



gence is confined to animals. All vegetables, however, do 

 not possess the building power ; it is apparently a property 

 belonging exclusively to green parts : and all animals do not 

 possess intelligence; but, on the contrary, it may be assumed 

 to be entirely absent from the lowest forms, while it appears 

 in obscure and gradual dawnings in others. 



In the region of the minute and simple beginnings of life, 

 the animal and vegetable kingdoms touch one another, and 

 there may even be a common territory including beings 

 which have no claim to be classed in one rather than the 

 other. But, growth and reproduction being the highest 

 functions of vegetable life, while intelligence is the highest 

 aim exhibited in the animal series, vegetable and animal 

 forms rapidly diverge as they become complex, so that those 

 of a highly developed description in the one kingdom cease 

 to have any resemblance to those of the other. 



5. The functions of animals may be enumerated as nutri- 

 tion, reproduction, sensory functions, and movement. The first 

 two of these, being equally characteristic of animals and 

 vegetables, are sometimes termed functions of organic life ; 

 while those varieties of the other two which constitute sensa- 

 tion and voluntary movement are distinguished as the func- 

 tions of animal life. In all, except the very simplest and 

 minutest creatures, special parts or groups of organs are 

 devoted to each of these different functions ; while, in addi- 

 tion, there is a large amount of structure, whose office is to 

 give protection or mechanical support to the rest of tho 

 body. 



Nutrition includes the various processes necessary for the 

 growth of the body and the maintenance of its substance. 

 Every living part of every living being undergoes change in 

 the particles of which it is composed, attracting and assimi- 

 lating to itself materials around it, and parting with others 

 which undergo decomposition ; and these processes of waste 

 and repair are in proportion to the activity of the part, 

 every manifestation of life being accompanied with chemical 

 and other changes. Thus a living being is a vortex, the par- 

 ticles of which are continually changing, while the form con- 

 tinues; and vital energy is a force correlative with mechanical, 

 chemical, and other forces found in the inorganic world. 



