MENTAL AND SOCIAL EVOLUTION 119 



the lowest to the highest. This system is adapted, in 

 each animal, to the support of such reflex action in the 

 lowest, as may be necessary to maintain its existence 

 and perpetuate its species ; and in the highest, in addi- 

 tion, to give it choice in the maintenance of all its com- 

 plex environment. This increase of choices constitutes 

 consciousness. In every animal there is a central organ 

 to the neural system to which every fibre runs, either 

 directly or indirectly. The complexity of this central 

 organ is in proportion to the number of fibres, and small 

 centers in the body, and its function is the determina- 

 tion of the responses necessary to be made to the most 

 important sensations received. But always there is. in 

 the simplest organism, at least, a reflex arc consisting of 

 a fibre running from every point of the body contiguous 

 with objectivity, or environment, to a center and from 

 that center to the muscle tissue, best adapted to make 

 the movement, to avoid an object, or respond to the 

 sensation. For example, hunger is the sensation of an 

 absence of the substance necessary to maintenance of 

 life. This sensation is carried by the reflex arc to the 

 central organ, and that sends it to the motor muscles, 

 putting them in proper motion to procure the 

 food that will allay the sensation. Most ani- 

 mals, being supplied with organic tools only, 

 that is, not being able to manufacture arti- 

 ficial tools, as man is, have no choice except to 

 use the tools nature has provided. These have a system 

 of nerves simple and adapted to the instructive control 

 of these natural tools. Their tools, such as wings, legs, 

 teeth, claws, beaks, etc., remaining unchangeable in 

 their shape and power during their lives, compel them 

 to do whatever -work they perform in only one and the 

 same way during life. Therefore they have a nervous 



