Licence: Public Domain Mark
Credit: A manual of medical diagnosis / by A.W. Barclay. Source: Wellcome Collection.
Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.
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![iif the group of symptoms be a very complex one. We sstill form our judgment from the aggregate, but we Lknow that one part is mucli more trustworthy and imore important than tlie remainder. One single symp- ttom even may, by its presence or absence, turn the 1 balance of evidence in favour of one disease, or exclude iianother ; but this view of its importance in connexion \Avith the whole group, of which it is but a ])art, is very cdifferent from the error already pointed out of regard- iing any sign as “ pathognomonic.” On this point correct :;general knowledge of disease can alone give jn-ecision tto our judgment; but it is also the province of a work con diagnosis to assign in some measure to each symp- itom its relative value. In the third place, the verification of the result mholly depends upon the accuracy of our knowledge cof the theory of disease. The evidence of symptoms l]>roperly arranged leads us so far in the right direction ifor discovering its true seat and nature ; but it docs mo more than point out a number of recpcirements with reference to particular organs, or to the system at IJarge, which any disease must be known a jjrlori to rfulfil, before we can admit it to be that which exists :in the case before us. From these considerations, I think it must be cvi- Ident that the moi-e numerous and the more simple the 'Symptoms are on which we have to decide, the more - certain must be our diagnosis. O Further illu.stration may perhaps he deemed unnecessary, luit my nieaning may l)e made more evident by comparing the inve.s- tigation of a case, to the properties of liguros in geometry. Sup- pose that through any four lixed points straiglit lines are drawn ■enclosiiig a ipiadrangular_ space; it is manifest that tlic uumher iiid variety ot figures whicli may he produced is very great; and t these figures are placed side hy side and compared with each )ther, they will only bo recognised as being four-sided figures, and ew j)orsons could find out that they had any other proj)crtv iu •omnion. But if through two of the ])oints (the first and tliird, or instance) the lines are always drawn parallel to each other, the iumb(!r of instances is at once much reduced, and this fact is mmediately recognised as being common to them all. If, in addi-](https://iiif.wellcomecollection.org/image/b24989812_0033.jp2/full/800%2C/0/default.jpg)
