5IO 



FALLACIES. 



may suflRce. But there may also he 

 non -observation of some material cir- 

 cum tances in instances which have 

 not been altogether overlooked — nay, 

 which may be the very instances on 

 which the whole superstructure of a 

 theory has been founded. As, in the 

 cases hitherto examined, a general 

 proposition was too rashly adopted, 

 on the evidence of particulars, true 

 indeed, but insufficient to support it ; 

 so in the cases to which we now turn, 

 the particulars themselves have been 

 imperfectly observed, and the singular 

 propositions on which the generalisa- 

 tion is grounded, or some at least of 

 those singular propositions, are false. 



Such, for instance, was one of the 

 mistakes committed in the celebrated 

 phlogistic theory — a doctrine which 

 accounted for combustion by the ex- 

 trication of a substance called phlo- 

 giston, supposed to be contained in all 

 combustible matter. The hjrpothesis 

 accorded tolerably well with superfi- 

 cial appearances : the ascent of flame 

 naturally suggests the escape of a sub- 

 stance ; and the visible residuum of 

 ashes, in bulk and weight, generally 

 falls extremely short of the combus- 

 tible material. The error was, non- 

 observation of an important portion 

 of the actual residue, namely, the 

 gaseous products of combustion. 

 When these were at last noticed and 

 brought into account, it appeared to 

 be an universal law that all substances 

 gain instead of losing weight by under- 

 going combustion ; and after the usual 

 attempt toaccommodatethe old theory 

 to the new fact by means of an arbi- 

 trary hypothesis, (that phlogiston had 

 the quality of positive levity instead 

 of gravity,) chemists were conducted 

 to the true explanation, namely, that 

 instead of a substance separated, there 

 was, on the contrary, a substance ab- 

 sorbed. 



Many of the absurd practices which 

 have been deemed to possess medi- 

 cinal efficacy have been indebted for 

 their reputation to non-observance 

 of some accompanying circumstance 

 which was the real agent in the cures 



ascribed to them. Thus, of the sym- 

 pathetic powder of Sir Kenelm Digby : 

 *' Whenever any wound had been in- 

 flicted, this powder was applied to the 

 weapon that had inflicted it, which 

 was, moreover, covered with ointment, 

 and dressed two or three times a day. 

 The wound itself, in the meantime, 

 was directed to be brought together, 

 and carefully bound up with clean 

 linen rags, but ab(»;e all, to he let alone 

 for seven days, at the end of which 

 period the bandages were removed, 

 when the wound was generally found 

 perfectly united. The triumph of the 

 cure was decreed to the mysterious 

 agency of the sympathetic powder 

 which had been so assiduously ap- 

 plied to the weapon, whereas it is 

 hardly necessary to observe that the 

 promptness of the cure depended on 

 the total exclusion of air from the 

 wound, and upon the sanative opera- 

 tions of nature not having received 

 any disturbance from the officious in- 

 terference of art. The result, beyond 

 all doubt, furjiished the first hint 

 which led surgeons to the improved 

 practice of healing wounds by what is 

 technically called the,^rs^ intention." * 

 " In all records," adds Dr. Paris, " of 

 extraordinary cures performed by mys- 

 terious agents, there is a great desire 

 to conceal the remedies and other 

 curative means which were simultane- 

 ously administered with them ; thus 

 Oribasius commends in high terms a 

 necklace of Paeony root for the cure 

 of epilepsy ; but we learn that he al- 

 ways took care to accompany its use 

 with copious evacuations, although he 

 assigns to them no share of credit in 

 the cure. In later times we have 

 a good specimen of this species of 

 deception presented to us in a work 

 on scrofula by Mr. Morley, written, 

 as we are informed, for the sole pur- 

 pose of restoring the much injured 

 character and use of the Vervain ; in 

 which the author directs the root of 

 this plant to be tied with a yard of 

 white satin riband round the neck,' 



* Pharmacologia, p. 23-24. 



