This classification, resting as it does upon merely superficial appearances, does not afford a certain means of separating the types, since factors, such as the depth of printing, the size of the patterns, and the prominence of secondary details may have an undue influence in the placing of a particular print in one or the other group.
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.
THE STANDARD PATTERNS OF PURKENJE
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.