gaging it from these, especially in reference to Consciousness, I have long hesitated before adopting it. But the advantages greatly outweigh the disadvantages. Sensibility has long been admitted to express the peculiar modes of reaction in plants and animals low down in the scale. No one hesitates to speak of a sensitive plant, or a sensitive surface. The tentacles of a polype are said to be sensitive; though probably no one thereby means that the polype has what psychologists mean by Consciousness. By employing the general term Sensibility to designate the whole range of reactions peculiar to the nerve-centres, when these special organs exist, it will be possible to interpret all the physiological and psychological phenomena observed in animals and men on one uniform method. The observed variations will then be referable to varieties in organisms.

85. Suppose, for illustration, an organism like the human except that it is wholly deficient in Sight, Hearing, Taste, and Smell. It has no sense but Touch- or the general reaction under contact with external objects. It will move on being stimulated, and will combine its movements differently under different stimulations. It will feel, and logically combine its feelings. But its mass of feeling will be made of far simpler elements than ours; its combinations fewer; and the contents of its Consciousness so very different from ours that we are unable to conceive what it will be like; we can only be sure that it will not be very like our own. This truncated organism will have its Sensibility; and we must assign this property to its central nerve-tissue, as we assign our own. If now we descend lower, and suppose an organism with no centres whatever, but which nevertheless displays evidence of Sensibility — feelings and combinations of movements we must then conclude that the property specialized in a particular tissue of the

highly differentiated organism is here diffused through

out.

It is obvious that the sensations or feelings of these supposed organisms will have a common character with the feelings of more highly differentiated organisms, although the modes of manifestation are so various. If we recognize a common character in muscular movements so various as the rhythmic pulsation of the heart, the larger rhythm of inspiration and expiration, the restless movements of the eye and tongue, the complexities of manipulation, the consensus of movements in flying, swimming, walking, speaking, singing, etc., so may we recognize a common character in all the varieties of sensation. The special character of a movement depends on the moving organ. The special character of a sensation depends on the sensory organ. Contractility is the abstract term which expresses all possible varieties of contraction. Sensibility- or Sentience - is the abstract term which expresses all possible varieties of sensation.

86. The view here propounded may find a more ready acceptance when its application to all physiological questions has been tested, and it is seen to give coherence to many scattered and hitherto irreconcilable facts. Meanwhile let a glance be taken at the inconsistencies of the current doctrine. That doctrine declares one half of the gray substance of the spinal cord to be capable only of receiving a sensitive stimulation, the other half capable only of originating a motor stimulation. We might with equal propriety declare that one half of a muscle is capable only of receiving a contractile stimulation, and the other half of contracting. The ingoing nerve, passing from the surface to the posterior part of the spinal cord, excites the activity of the gray substance into which it penetrates; with the anterior part of this gray substance

an outgoing nerve is connected, and through it the excitation is propagated to a muscle: contraction results. Such are the facts. In our analysis we separate the sensory from the motor aspect, and we then imagine that this ideal distinction represents a real separation. We suppose a phenomenon of Sensibility independent of a phenomenon of Contractility-suppose the one to be "transformed into the other and we then marvel "how during this passage the excitation changes its nature."

"

87. Before exerting ingenuity in explaining a fact, it is always well to make sure that the fact itself is correctly stated. Does the neural excitation change its nature in passing from the posterior to the anterior gray substance? I can see no evidence of it. Indeed the statement seems to confound a neural process with a muscular process. The neural process is one continuous excitation along the whole line of ingoing nerve, centre, and outgoing nerve, which nowhere ceases or changes into another process, until the excitation of the muscle introduces a new factor. So long as the excitation keeps within the nerve-tissue, it is one and the same process of change; its issue in a contraction, a secretion, or a change in the conditions of consciousness, depends on the organs it stimulates.

88. I have already called attention to the artificial nature of all our distinctions, and the necessity of such artifices. They are products of that

"Secondary power

By which we multiply distinctions, then
Deem that our puny boundaries are things

That we perceive, and not that we have made."+

The distinction of Central and Peripheral systems is not

*CLAUDE BERNARD, Système Nerveux, 1858, I. 349.

+ WORDSWORTH, The Prelude.

simply anatomical, it has a physiological justification in this, that the Central System is the organ of connection. Any one part of it directly excited by an ingoing nerve propagates that excitation throughout the whole central mass, and thus affects every part of the organism. Therefore we place Sensibility in it.

But this general Property subserves various Functions, according as the Central System is variously related to different organs. This fact has given rise to the idea that different portions of the cerebro-spinal axis have different properties which is a serious error. What is certain is

that the Cerebrum must have a different function from that of the Thalami, and the Cerebellum one different from the Medulla Oblongata; while that of the Medulla Spinalis is different from all. Precisely on the same grounds that a muscle-nerve has a different office from a skin-nerve, or the pneumogastric from the acoustic. But all nerves have one Neurility in common; all centres have one Sensibility in common.

CHAPTER V.

ACTION WITHOUT NERVE-CENTRES.

89. IT has long been one of the unquestioned postulates of Physiology that no nerve-action can take place without the intervention of a centre; and as a corollary, that all movement has its impulse-reflex or volitional from a centre.* The postulate rests on the assumption that nerves derive their "force" from their centre. This assumption we have seen to be erroneous. Yet, in consequence of its acceptance, experimenters have failed to notice the many examples of nerve-action independent of centres. Indeed, except Schiff, Goltz, and Engelmann, I can name no one who has ventured to suggest that movements may be excited through nerves without the co-operation of centres; † nor have even they explicitly formulated the conclusion to which their observations point.

It is true that the majority of muscular movements are determined by a reflex from centres; and that any break

"On peut dire que toujours un phénomène de mouvement reconnait pour point de départ une impression sensitive." - CLAUDE BERNARD, I. 267.

+ Since this was written Prof. MICHAEL FOSTER and Mr. DEW SMITH have published their very important researches on the motions of the heart, which establish beyond a doubt that, in the molluscs at least, there is no co-operation of either centre or nerve. Proceedings of the Royal Society, 18th March, 1875. (See also Studies from the Physiological Laboratory of Cambridge, Part II., 1876.) Mr. Foster knows that I had independently, and from a totally different line of research, arrived at the same conclusion respecting the heart's movement.