DEPENDENCE OF MENTAL ACTIONS UPON SENSATIONS. 477 



instrument of the Psychical* powers, which are the distinguishing 

 attribute of the Animal. It has been already pointed out, that the pos- 

 session of Consciousness (or of the capability of receiving sensations), 

 and the power of executing Spontaneous Movements (that is, movements 

 which are not immediately dependent upon external stimuli), constitute 

 the essential features in which the Animal differs from the Plant. All 

 the other differences in structure, that respectively characterize these 

 two classes of living beings, are subordinate to this one leading distinc- 

 tion, the presence of a Nervous system, and of its peculiar attributes 

 in the one,- and its absence in the other. Now when we attempt to 

 analyze those peculiar attributes, we may resolve them, like the pro- 

 perties of the material body, into different groups. We find that the 

 first excitement of all mental changes, whether these involve the action 

 of the feelings or of the reason, depends upon sensations ; which are 

 produced by impressions made upon the nerves of certain parts of the 

 body, and are conveyed by these to a particular ganglionic centre, 

 which is termed the sensorium, being the part in which Sensation, or 

 the capability of feeling external impressions, especially resides. 



845. Now there are numerous actions, especially among the lower 

 Animals, which seem to be as far removed from the influence of the 

 Will, and as little directed by Intelligence, as the Reflex movements 

 themselves; but which, nevertheless, depend upon sensation for their 

 excitement. The sensation may immediately direct the movement, and 

 may call the muscular apparatus into action in such a manner, as, with- 

 out any calculation of consequences, any intentional adaptation of means 

 to ends, any exertion of the reason, or any employment of a discrimi- 

 nating Will, to produce an action, or train of actions, as directly and 

 obviously adapted to the well-being of the individual, as we have seen 

 those of the reflex character to be. Of this we have an excellent 

 example in the act of Sneezing ; the purpose of which is obviously to 

 expel from the nasal passages those irritating matters, the sense of 

 whose presence excites the complicated assemblage of muscular move- 

 ments concerned in the operation. This class of actions may be appro- 

 priately termed the Consensual; and under it we may include most of 

 those purely instinctive actions of the lower animals, -which, being 

 prompted by sensations, cannot be assigned to the reflex group. These 

 seem to make up, with the reflex, nearly the whole of the Animal 

 functions in many tribes ; but they are found to be gradually brought 

 under the domination of the Intelligence and Will, as we rise towards 

 Man, in whom those faculties are most strongly developed, so as to 

 keep the Consensual as well as the Reflex actions quite in subordination 

 to the more elevated purposes of his existence. Closely allied, however, 

 to these, are the purely JSmotional movements ; in which the sensation 

 excites a mental feeling or impulse, that reacts upon the muscular 

 system without giving rise to any distinct idea, and consequently 

 without having called the intellect and will into exercise. In fact, 

 these emotional movements are often performed in opposition to the 



* This term, derived from the Greek 4 w ;t> is used to designate the sensorial and 

 mental endowments of Animals, in the most comprehensive acceptation of those terms. 



