After numerous futile attempts to make use of Purkenje's system, Sir Francis Galton discarded it in favour of a system in which the triangular space or spaces found in the majority of finger impressions was made the basis of classification. Starting upon the two divergent ridges from these spaces an outline was then drawn as far as it could be traced, the course of each ridge being followed with minute fidelity. In this way a series of sharply-defined outline figures were obtained. [Illustration: THE STANDARD PATTERNS OF PURKENJE] [Illustration: CORES OF THE ABOVE PATTERNS 1. Transverse flexures 2. Central longitudinal stria 3. Oblique stria 4. Oblique sinus 5. Almond 6. Spiral 7. Ellipse 8. Circle 9. Double Whorl _By kind permission of Messrs. Macmillan & Co., Ltd._] The various patterns may, as a rule, be classified into the three main groups of arches, loops and whorls, while some of the transitional forms may be grouped under more than one of these heads. Other patterns, again, which are of rare occurrence, are not suitable for inclusion in any of the three groups. A system of indexing based upon this method of classification was also devised in which letters represented the varieties of patterns. Thus _a, a, a_ indicate that the outline upon the fore, middle and ring fingers consists of arches, while _a, w, l_ indicate an arch upon the forefinger, a whorl upon the middle finger, and a loop upon the ring finger. The letters _i_ and _o_ are also used, the former indicating a loop with an inward slope and the latter one with an outer slope upon the forefinger. The possible variations in such a classification of the impressions of the three fingers of the right hand cannot exceed thirty-six, and a thousand prints may therefore be indexed into one of these thirty-six groups. Subdivisions of these main groups may then be based upon the characteristics of the prints of the fingers of the other hand and of the thumbs, while differences in the cores of the patterns afford a means of forming smaller divisions of the loop patterns. From observations of the 5,000 prints of 500 individuals Sir Francis Galton found that arches were present in 6·5 per cent.; loops in 67·5 per cent.; and whorls in 26·0 per cent. Each digit and hand, however, had its own peculiarities, and the variations in the percentage of arches upon different digits ranged from 1 to 17; that of the loops from 53 to 90; and that of the whorls from 13 to 45. Loops occurred with most frequency upon the little finger and then upon the middle finger, while whorls were rarely met with upon these fingers, but were of common occurrence upon the thumb and ring finger.