On the Perceptive Power of the Spinal Chord, as Manifested by Cold-Blooded Animals.
George Paton · PubMed · 1846
On the perceptive power of the Spinal Chord, as manifested by cold blooded animals.By George Paton, M. D.-Physiologists have divided the movements of the animal economy into voluntary and in voluntary.The former order comprises all those movements that are under our power and control; the latter, those that take place without our will, and independent of our agency.But a voluntary movement may be either of a spontaneous character, that is' , it may originate in the mind from a particular train of ideas, and independent of any ex ternal stimulus operating to suggest it; or it may depend on an im pression produced on the surface of the body, exciting the individual to the performance of the action, as when we withdraw a limb from any irritation to which it is exposed.But in both cases there is the utmost freedom in the movement, and every element essential to constitute it voluntary.In the one case, the mind is incited to the action by a train of thought connected with sensations and emotions which we had al ready felt and experienced.In the other, the stimulus, being immedi ately present to the senses, produces a feeling or emotion which leads to the performance of the action.It thus appears that the principle which constitutes an action voluntary is not the manner in which it is excited, but the mode in which it is performed,-a fact which will enable us more clearly to understand the nature of the movements per formed by animals after removal of the cerebrum, and see how far such phenomena indicate sensation and the power of voluntary motion in an animal; or are to be accounted for, as maintained by some physiologists, on the principle of a reflex or excito-motory action of the spinal chord.As this is a question which involves general principles of great im portance in reference to the functions of the nervous system, we shall, in determining the nature of the phenomena observed, endeavour to show, according to the strict and philosophical import of the terms, that not merely sensation but perception enters into the character of the movements,-an indubitable proof that the animal can exercise control over its muscles, or has the power of regulating its movements to the attainment of a definite object." Sensation is a name given by philosophers to an act of mind, which may be distinguished from all others by this, that it hath no object dis tinct from the act itself."It is simply expressive of the pain or plea sure felt by the individual at the moment, but has no reference to the canse or irritation that produces it.When I say that I am suffering pain, I speak of a mere feeling or sensation of the mind, without re lation to any external object or source from which the pain originates.And this is all that is to be understood by the term sensation.It is ex pressive of the state of mind, or manner in which I am affected at the moment, but nothing more,-in which sense, sensation and feeling are of exactly the same import.* "The microscope does not confirm the opinion of E. H. Weber, Bellingeri, and Grainger, that some fibres pass straightway to the central substance of the chord."-Mr.Paget's Report, Brit, and Foreign Med.Rev. Messrs.