Of these conflicting opinions I can have no difficulty in at any rate rejecting that of Wegner; for the clinical phenomena of the complications attending trigeminal neuralgia, such as they are described in my last chapter (and could have been described at much greater length), seem to me utterly to exclude vaso-motor spasm except as a temporary phenomenon at the commencement of the attacks of acute pain. Vaso-motor palsy undoubtedly is very often present, in fact every attack of neuralgia of a certain severity is thus complicated; and there is no reason to doubt that this paralysis could be caused by lesions within the medulla. Are we, then, to admit functions of active dilatation of vessels, and active impulse to secretion in certain fibres of the fifth? It is necessary at any rate to clear the ground in one respect: it must not be supposed that I for a moment entertain the idea that there can be direct active dilatation, _i. e._, that there can be any system of muscular fibres (and nerve-fibres stimulating them) whose office is to open the calibre of the vessels; the idea is wildly improbable--in fact almost inconceivable by any one who reflects on the necessary machinery--and there is not a single observed anatomical fact to give it support. If, then, I speak of the possibility of "active" dilatation, it must be understood that I refer to a theory of "inhibition," which supposes certain fibres to be gifted with the power of paralyzing or inhibiting the vaso-motor nerves. It is my duty to speak with all reasonable reserve on that most difficult _quæstio vexata_, the existence of special inhibiting systems of nerves, and the extent to which a double series of opposed nervous actions is generalized in the body; but it is impossible to avoid the subject altogether, and I offer the following remarks, with deference, to our professional physiologists. The strongest instances of the apparent inhibiting action are probably afforded by the _nervi erigentes_, as shown by Loven, the cardiac depressor, by Ludwig and Cyon, and the splanchnics (upon the intestine), by Pfluger. But there is not a single one of these examples that has not been challenged by experimenters of repute. Thus the theory of the distinctive restraint-action of the splanchnics upon the intestine, and of the vagus upon the heart, has been especially controverted by Piotrowski, who, indeed, rejects the whole theory of special inhibitory nerves.[25] And, from another point of view, Mr. Lister long ago attacked the views of Pfluger, maintaining that it was possible to produce exactly opposite effects through the medium of the very same nerves, according as the experimental irritation applied to them was weak or strong. To Dr. Handfield Jones[26] this seems a still unanswerable objection to the inhibitory theory. And in the remarkably able and judicial summary of the "Physiology and Pathology of the Sympathetic or Ganglionic System,"[27] by Dr. Robert T. Edes, a less