Volume 1

An introduction to medical literature, including a system of practical nosology, intended as a guide to students, and an assistant to practitioners. Together with detached essays on the study of physic, on classification, on chemical affinities, on animal chemistry, on the blood, on the medical effects of climates, on the circulation, and on palpitation. / By Thomas Young.

  • Thomas Young
Date:
1823
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to medical literature, including a system of practical nosology, intended as a guide to students, and an assistant to practitioners. Together with detached essays on the study of physic, on classification, on chemical affinities, on animal chemistry, on the blood, on the medical effects of climates, on the circulation, and on palpitation. / By Thomas Young. Source: Wellcome Collection.

    63/696 (page 31)
    The idea of the genus must‘occur first to the mind: [ But this observation can only apply to the Latin lan- guage: and in chemical names, it appears to be of little con- sequence how the component parts of a salt are presented to the mind: nor is it easy to say whether the term potassae sulfas implies that the sulfates, or the salts of potass, are to be considered as forming one genus. |] . 286. <A specific name without the generic is like a bell without a clapper. 287. The specific name must not be united to the generic as a termination. 288. A genuine specific character is either synoptic or essential. 289. <A synoptic specific character distinguishes the spe- cies of the genus by successive subdivisions into two portions. In large genera such subdivisions are often indispensable. 290. An essential specific character exhibits a single dis- tinction, appropriate to one species only. 291. The shorter a specific character can be made, the better, provided that it be sufficient. The number of words admitted in a specific character ought never to exceed twelve: some limit must be laid down, and this number appears to be sufficient. Suppesing a substantive _and an adjective to be required for each subdivision of the genus into two collateral parts only, as in a synoptic charac- ter, which is the most unfavourable supposition, we may dis- tinguish 100 species of the same genus by “* 12” words, thus, Aua,50; Bb, 25; Cc,13; Dd,7; Ee,4; Ff,2; Gg, 1. [In fact, however, 14 words are here supposed ; but it can seldom happen either that the species of a genus are so nu= merous, or the subdivision so little diversified. 'Thus.-we might easily find cases in which two substantives, with ten different adjectives applied to each, might abundantly distinguish 100 species, employing only four words at a time ; and experience shows that twelve words are almost universally sufficient. } For want of this conciseness, all the old specific characters, which exhibit descriptions instead of distinctions, are to be held in abhorrence.