CHAPTER IV 

 ANIMAL BEHAVIOUR 



By animal behaviour is meant the whole activities, with their 

 meanings, of the organism regarded as a unitary thing. But it 

 is convenient first to dissociate these activities in an arbitrary 

 way. That has partially been done in Section 12a, w^here the 

 effector organs, that is the system of limbs, appendages, teeth, 

 claws, etc., were summarily described, and also in Sections 12, 

 b-e, where the energizing organs, that is, those of alimentation, 

 respiration, etc., were also described : these latter organs must 

 be regarded as subserving the effector ones. 



First, in this chapter, w^e consider the organs of sensation and 

 integration, that is, the receptors, the peripheral nervous system 

 and the nervous centres. Thus we complete the account of 

 the means of behaviour. Next we take up the study of the 

 purposes, and the grades of complexity of behaviouristic activity 

 in the animal kingdom and lastly we have to consider behaviour 

 in itself and apart from any analytical discussion of its nature. 

 It is to be noted that throughout we restrict our study to animal 

 organisms. Something of the nature of behaviour, as we think 

 about it in animals, is also to be seen among plant organisms 

 and, of course, in those Protista which we regard almost indifTer- 

 ently as either plant or animal. But the subject is one that 

 applies almost entirely to the animal kingdom. 



/. THE ORGANS OF THE " SENSORI-MOTOR " SYSTEM 



These are the Receptors, or " sense-organs " ; the afferent 

 and efferent nerves, the central ganglia and the effector organs. 



39. ON THE RECEPTOR ORGANS 



The whole substance of the body of an animal is irritable, 

 that is, it respojids (changes, contracts, etc.) when it is stimulated 



TOT 



