440 PHYSIOLOGY CHAP. 



adaptation to circumstances, their choice of the means best suited 

 to an end. The physiologist makes constant use of this test 

 when he compares the degree of intelligence in different animals 

 in the zoological scale, and attempts to define the psychical or the 

 purely mechanical character of the functions of the various nerve- 

 centres. In this connection we may refer again to the movements 

 of which the spinal frog (Vol. III. pp. 335-341) and the bulbo- 

 spinal animal (pp. 351-5) are capable, which led us to conclude 

 that consciousness is not localised exclusively in the brain, but is 

 diffused throughout the cerebro-spinal axis ; and that an animal in 

 which the brain-centres are mutilated is not deprived of sensi- 

 bility and of the power of carrying out many reflex acts which 

 present a teleological character that is, are adapted to circum- 

 stances and vary with variation of environment, as in removing 

 injurious stimuli. 



Strictly speaking, these acts cannot be called conscious, 

 because the brainless animal has no perceptions, representations, 

 or volitions which are the condition of states of consciousness. 

 Still granting the teleological responsive and adaptive character 

 of its actions it must be vaguely aware of elementary cutaneous 

 and muscular sensations, which suffice to make up a lower form 

 of consciousness (Pfliiger's so-called spinal animal), consisting in 

 a synthesis of sensations which are able, however indefinite and 

 rudimentary, to initiate co-ordinated responsive acts, adapted to 

 a purpose, and therefore of the same type as conscious and 

 voluntary acts. 



In the ordinary language of physiology the expressions 

 " unconscious sensations," " unconscious feelings/' frequently recur 

 and seem to be nonsense and a contradiction in terms, seeing that 

 sensations and feelings are fundamental elements in conscious- 

 ness ; but they become intelligible and practically justifiable in so 

 far as they signify that there are different forms and degrees in 

 consciousness. We can readily distinguish the states of conscious- 

 ness that form the content of the ego, on which we direct our 

 attention by taking these states as the objects of our thought, 

 from the active states of sensibility which operate outside the 

 range of attention. These last may justly be termed in a broad 

 sense unconscious sensations and feelings because they lie at the 

 threshold of consciousness, i.e. of the sensorial ego. 



These nervous processes, accordingly, have the same specific 

 characters, produce the same results, and fulfil the same functions 

 as conscious sensory processes ; it follows that they come into the 

 range of mental life, and even constitute by far the largest part of 

 the integral content of the mind. 



In support of this theory it is easy to show that conscious and 

 unconscious states can be reciprocally transformed into each 

 other, and that there is a constant exchange between them. 



