What are these conditions of existence? or, more simply, what is pain in its nature? At the present time there are two distinct doctrines on this point: one, which counts few adherents, regards physical pain as properly a _sensation_; the other, more generally admitted, regards it as a _quality_ of sensation, or more correctly, as an accompaniment, a concomitant.[27] ----- Footnote 27: The debates on this subject have chiefly been carried on by American psychologists. See Rutgers Marshall, _Pain, Pleasure, and Æsthetics_ (1895); Nichols, “Origin of Pleasure and of Pain” (_Philosophical Review_, i. pp. 403 and 518); Strong, “Psychology of Pain” (_Psychological Review_, July 1895, and for criticisms and replies, Sept. and Nov. 1895, Jan. 1896); Luckey, “Some Recent Studies of Pain” (_Am. Journal of Psychology_, Oct. 1895). ----- The first, though recent in its complete form, is not without antecedents. It found a momentary support in the supposed discovery of pain-bearing nerves. Nichols, one of the promoters of this hypothesis, has developed it in this direction; but the attempt has proved futile. Strong, one of its warmest partisans, supported himself on other grounds. In his opinion the difficulty arises from the ambiguity of the word pain, which may mean two things—displeasure (_Unlust_), or physical pain in the positive sense. He reduces the latter to cuts, pricks, burns—in short, to those pains that affect the skin. It is, in his opinion, strictly a sensation like blue or red—not an attribute, but a substantive. The pain of a burn, for instance, is a mixture of two sensations, heat and pain. General sensibility is composed of four kinds of sensibility: touch, heat, cold, and pain. Each can be abolished separately. Cocaine and chloroform suppress pain, not touch; saponine suppresses touch, not pain; syringomyelia destroys sensibility to pain and heat, not touch; in some forms of neuritis there is suppression of touch without analgesia. These various facts are invoked as the chief arguments in favour of the hypothesis of pain-sensation, though they may all be explained also by the other doctrine.