ON NOSOLOGY. 455 



many other fevers, and therefore no ways characteristic. This, 

 however, is not so common a fault as the contrary, a deficient 

 character from an accidental imitation of the botanists, who, 

 when they have a number of species to name, study to 

 make the specific character as short as possible ; but, in Noso- 

 logy, by endeavouring to be short, we have become obscure 

 and imperfect. For however long the character may be, if all 

 its parts are necessary marks, they are to be admitted. Let us 

 take the ninety-second genus of Sauvages, and see what char- 

 acter he has given to Variola : ' Eruptio pustularum phleg- 

 monodearum in suppurationem tendentium.' This applies to 

 the itch as well as to the smallpox, and the imperfection will 

 scarcely be supplied by his general character of Exanthemata 

 6 Eruptiones cutaneae cum pyrexia saepius maligna, quandoque 

 lenta, 1 unless the duration and fixed time of the eruption is men- 

 tioned to distinguish it from other exanthemata. Through the 

 whole of Linnaeus 1 arrangement particularly, these deficient 

 characters are evident ; and as hardly any disease is distinguished 

 by a single pathognomonic symptom, but all by a concourse of 

 symptoms, I would undertake to shew, that whenever a char- 

 acter is very short, it is artificial and not natural. 



A second rule is, that the marks which we employ should be 

 sufficiently evident, and, if possible, constantly present at every 

 period of the disease ; these at least are the most characteristic. 

 Nosologists transgress against this rule when the marks are 

 taken from the duration, and much more from the event of the 

 disease. To affirm that a disease is a fatal one, is indeed a part 

 of its history, but cannot serve as a character when we first view 

 the disease. Of this fault we have examples in the character 

 of fevers, by Sauvages and Linnaeus, who have distinguished 

 the genera entirely by their duration. Thus the Ephemera 

 terminates within three or four days, the Synochus in two or 

 three weeks ; the Typhus extends to three weeks, &c. ; but these 

 are no characters at all ; and, in order to distinguish these dis- 

 eases, it was absolutely necessary to employ other characters. 

 In general, therefore, the terms acuta, chronica, lenta, are im- 

 proper and insufficient in Nosology. I must observe, how- 

 ever, that it is impossible to avoid contravening this rule, in 

 some measure, in certain cases in which the diseases are dis- 





