206 Life and Letters of Francis Galton
reunite forming the eye of a needle, or there may be an imperfect eye. The main point is that the core is not a simple rod; the several conditions do not need symbolising severally, they are all expressed by f.
c represents the case when the core within the loop is a second staple wholly detached from the outer staple which curves round it.
Galton uses still further symbols in his secondary classification-k, v, x, y, and three others to denote conditions of the print itself, namely: d, t and'. d marks a damaged print, either owing to the condition of the finger, or to the printing. If the print be wholly unreadable, then d is inserted in its proper place in the primary 10 symbols; if the print be only partially damaged, then d is to be used as a suffix. t denotes the scar of a cut, and should be used, however small the scar may be, as it is a valuable means of identification. * denotes that a portion of the finger has been more or less smashed, and should be combined with d.
Of the other four symbols x denotes that there is something very peculiar or questionable about the pattern.
v indicates what Galton terms an invaded loop. Usually the ridges enter through the open mouths of the loop, curve round and take their exits
Fig. 39. Secondary Classification of Loops, Galton's y and v. FOUR FORMS of Loop (one delta) tj
Fig. 40. Secondary Classification of Loops, Galton's y, v and k.
parallel to their entrances. Sometimes, however, a system of ridges instead of entering from the mouth, springs out from one of the sides and destroys the symmetry of the pattern. Such a loop is an "invaded loop" and symbolised by v. Galton holds y to be one of the most generally useful of suffixes ; it is the formation in the inner part of the loop of an eyed form, - In the ordinary loop the ridges after turning back run parallel; in the eyed loop they reunite after recurving and enclose a minute plot. y must be distinguished from f, which latter is an island or approximate island in a central rod.
Finally k denotes a curvature sometimes affecting the whole of a loop, turning it into more or less of a solid hook, i.e. not a hook formed by a single