CHAPTER V
PATTERNS: THEIR OUTLINES AND CORES
The patterns on the thumb and fingers were first discussed at length by Purkenje in 1823, in a University Thesis or _Commentatio_. I have translated the part that chiefly concerns us, and appended it to this chapter together with his corresponding illustrations. Subsequent writers have adopted his standard types, diminishing or adding to their number as the case may be, and guided as he had been, by the superficial appearance of the lineations.
In my earlier trials some three years ago, an attempt at classification was made upon that same principle, when the experience gained was instructive. It had seemed best to limit them to the prints of a single digit, and the thumb was selected. I collected enough specimens to fill fourteen sheets, containing in the aggregate 504 prints of right thumbs, arranged in six lines and six columns (6 x 6 x 14 = 504), and another set of fourteen sheets containing the corresponding left thumbs. Then, for the greater convenience of study these sheets were photographed, and enlargements upon paper to about two and a half times the natural size made from the negatives. The enlargements of the right thumb prints were reversed, in order to make them comparable on equal terms with those of the left. The sheets were then cut up into rectangles about the size of small playing-cards, each of which contained a single print, and the register number in my catalogue was entered on its back, together with the letters L. for left, or R.R. for reversed right, as the case might be.
On trying to sort them according to Purkenje's standards, I failed completely, and many analogous plans were attempted without success. Next I endeavoured to sort the patterns into groups so that the central pattern of each group should differ by a unit of "equally discernible difference" from the central patterns of the adjacent groups, proposing to adopt those central patterns as standards of reference. After tedious re-sortings, some sixty standards were provisionally selected, and the whole laid by for a few days. On returning to the work with a fresh mind, it was painful to find how greatly my judgment had changed in the interim, and how faulty a classification that seemed tolerably good a week before, looked then. Moreover, I suffered the shame and humiliation of discovering that the identity of certain duplicates had been overlooked, and that one print had been mistaken for another. Repeated trials of the same kind made it certain that finality would never be reached by the path hitherto pursued.
On considering the causes of these doubts and blunders, different influences were found to produce them, any one of which was sufficient by itself to give rise to serious uncertainty. A complex pattern is capable of suggesting various readings, as the figuring on a wall-paper may suggest a variety of forms and faces to those who have such fancies. The number of illusive renderings of prints taken from the same finger, is greatly increased by such trifles as the relative breadths of their respective lineations and the differences in their depths of tint. The ridges themselves are soft in substance, and of various heights, so that a small difference in the pressure applied, or in the quantity of ink used, may considerably affect the width of the lines and the darkness of portions of the print. Certain ridges may thereby catch the attention at one time, though not at others, and give a bias to some false conception of the pattern. Again, it seldom happens that different impressions of the same digit are printed from exactly the same part of it, consequently the portion of the pattern that supplies the dominant character will often be quite different in the two prints. Hence the eye is apt to be deceived when it is guided merely by the general appearance. A third cause of error is still more serious; it is that patterns, especially those of a spiral form, may be apparently similar, yet fundamentally unlike, the unaided eye being frequently unable to analyse them and to discern real differences. Besides all this, the judgment is distracted by the mere size of the pattern, which catches the attention at once, and by other secondary matters such as the number of turns in the whorled patterns, and the relative dimensions of their different parts. The first need to be satisfied, before it could become possible to base the classification upon a more sure foundation than that of general appearance, was to establish a well-defined point or points of reference in the patterns. This was done by utilising the centres of the one or two triangular plots (see Plate 4, Fig. 8, ~2~, ~3~, ~4~) which are found in the great majority of patterns, and whose existence was pointed out by Purkenje, but not their more remote cause, which is as follows:
The ridges, as was shown in the diagram (Plate 3) of the palm of the hand, run athwart the fingers in rudely parallel lines up to the last joint, and if it were not for the finger-nail, would apparently continue parallel up to the extreme finger-tip. But the presence of the nail disturbs their parallelism and squeezes them downwards on both sides of the finger. (See Fig. 8, ~2~.) Consequently, the ridges that run close to the tip are greatly arched, those that successively follow are gradually less arched until, in some cases, all signs of the arch disappear at about the level of the first joint (Fig. 8, ~1~). Usually, however, this gradual transition from an arch to a straight line fails to be carried out, causing a break in the orderly sequence, and a consequent interspace (Fig. 8, ~2~). The topmost boundary of the interspace is formed by the lowermost arch, and its lowermost boundary by the topmost straight ridge. But an equally large number of ducts exist within the interspace, as are to be found in adjacent areas of equal size, whose mouths require to be supported and connected. This is effected by the interpolation of an independent system of ridges arranged in loops (Fig. 8, ~3~; also Plate 5, Fig. 9, _a_, _f_), or in scrolls (Fig. 8, ~4~; also Fig. 9, _g_, _h_), and this interpolated system forms the "pattern." Now the existence of an interspace implies the divergence of two previously adjacent ridges (Fig. 8, ~2~), in order to embrace it. Just in front of the place where the divergence begins, and before the sweep of the pattern is reached, there are usually one or more very short cross-ridges. Their effect is to complete the enclosure of the minute triangular plot in question. Where there is a plot on both sides of the finger, the line that connects them (Fig. 8, ~4~) serves as a base line whereby the pattern may be oriented, and the position of any point roughly charted. Where there is a plot on only one side of the finger (Fig. 8, ~3~), the pattern has almost necessarily an axis, which serves for orientation, and the pattern can still be charted, though on a different principle, by dropping a perpendicular from the plot on to the axis, in the way there shown.
These plots form corner-stones to my system of outlining and subsequent classification; it is therefore extremely important that a sufficient area of the finger should be printed to include them. This can always be done by slightly _rolling_ the finger (p. 39), the result being, in the language of map-makers, a cylindrical projection of the finger (see Plate 5, Fig. 9, _a-h_). Large as these impressions look, they are of the natural size, taken from ordinary thumbs.
_The outlines._--The next step is to give a clear and definite shape to the pattern by drawing its outline (Fig. 9). Take a fine pen, pencil, or paint brush, and follow in succession each of the two diverging ridges that start from either plot. The course of each ridge must be followed with scrupulous conscientiousness, marking it with a clean line as far as it can be traced. If the ridge bifurcates, always follow the branch that trends towards the middle of the pattern. If it stops short, let the outline stop short also, and recommence on a fresh ridge, choosing that which to the best of the judgment prolongs the course of the one that stopped. These outlines have an extraordinary effect in making finger markings intelligible to an untrained eye. What seemed before to be a vague and bewildering maze of lineations over which the glance wandered distractedly, seeking in vain for a point on which to fix itself, now suddenly assumes the shape of a sharply-defined figure. Whatever difficulties may arise in classifying these figures, they are as nothing compared to those experienced in attempting to classify unoutlined patterns, the outlines giving a precision to their general features which was wanting before.
After a pattern has been treated in this way, there is no further occasion to pore minutely into the finger print, in order to classify it correctly, for the bold firm curves of the outline are even more distinct than the largest capital letters in the title-page of a book.
A fair idea of the way in which the patterns are distributed, is given by Plate 6. Eight persons were taken in the order in which they happened to present themselves, and Plate 6 shows the result. For greater clearness, colour has been employed to distinguish between the ridges that are supplied from the inner and outer sides of the hand respectively. The words right and left _must be avoided_ in speaking of patterns, for the two hands are symmetrically disposed, only in a reversed sense. The right hand does not look like a left hand, but like the reflection of a left hand in a looking-glass, and _vice versa_. The phrases we shall employ will be the _Inner_ and the _Outer_; or thumb-side and little-finger side (terms which were unfortunately misplaced in my memoir in the _Phil. Trans._ 1891).
There need be no difficulty in remembering the meaning of these terms, if we bear in mind that the great toes are undoubtedly innermost; that if we walked on all fours as children do, and as our remote ancestors probably did, the thumbs also would be innermost, as is the case when the two hands are impressed side by side on paper. Inner and outer are better than thumb-side and little-finger side, because the latter cannot be applied to the thumbs and little fingers themselves. The anatomical words radial and ulnar referring to the two bones of the fore-arm, are not in popular use, and they might be similarly inappropriate, for it would sound oddly to speak of the radial side of the radius.
The two plots just described will therefore be henceforth designated as the Inner and the Outer plots respectively, and symbolised by the letters I and O.
The system of ridges in Fig. 10 that comes from the inner side "I" are coloured blue; those from the outer "O" are coloured red. The employment of colour instead of variously stippled surfaces is of conspicuous advantage to the great majority of persons, though unhappily nearly useless to about one man in every twenty-five, who is constitutionally colour-blind.
It may be convenient when marking finger prints with letters for reference, to use those that look alike, both in a direct and in a reversed aspect, as they may require to be read either way. The print is a reversed picture of the pattern upon the digit that made it. The pattern on one hand is, as already said, a reversed picture of a similar pattern as it shows on the other. In the various processes by which prints are multiplied, the patterns may be reversed and re-reversed. Thus, if a finger is impressed on a lithographic stone, the impressions from that stone are reversals of the impression made by the same finger upon paper. If made on transfer paper and thence transferred to stone, there is a re-reversal. There are even more varied possibilities when photography is employed. It is worth recollecting that there are twelve capital letters in the English alphabet which, if printed in block type, are unaffected by being reversed. They are A.H.I.M.O.T.U.V.W.X.Y.Z. Some symbols do the same, such as, * + - = :. These and the letters H.O.I.X. have the further peculiarity of appearing unaltered when upside down.
_Lenses._--As a rule, only a small magnifying power is needed for drawing outlines, sufficient to allow the eye to be brought within six inches of the paper, for it is only at that short distance that the _minutiae_ of a full-sized finger print begin to be clearly discerned. Persons with normal sight, during their childhood and boy- or girlhood, are able to read as closely as this without using a lens, the range in adjustment of the focus of the eye being then large. But as age advances the range contracts, and an elderly person with otherwise normal eyesight requires glasses to read a book even at twelve inches from his eye. I now require much optical aid; when reading a book, spectacles of 12-inch focus are necessary; and when studying a finger print, 12-inch eye-glasses in addition, the double power enabling me to see clearly at a distance of only six inches. Perhaps the most convenient focus for a lens in ordinary use is 3 inches. It should be mounted at the end of a long arm that can easily be pushed in any direction, sideways, backwards, forwards, and up or down. It is undesirable to use a higher power than this unless it is necessary, because the field of view becomes narrowed to an inconvenient degree, and the nearer the head is to the paper, the darker is the shadow that it casts; there is also insufficient room for the use of a pencil.
Every now and then a closer inspection is wanted; for which purpose a doublet of 1/2-inch focus, standing on three slim legs, answers well.
For studying the markings on the fingers themselves, a small folding lens, sold at opticians' shops under the name of a "linen tester," is very convenient. It is so called because it was originally constructed for the purpose of counting the number of threads in a given space, in a sample of linen. It is equally well adapted for counting the number of ridges in a given space.
* * * * *
Whoever desires to occupy himself with finger prints, ought to give much time and practice to drawing outlines of different impressions of the same digits. His own ten fingers, and those of a few friends, will furnish the necessary variety of material on which to work. He should not rest satisfied until he has gained an assurance that all patterns possess definite figures, which may be latent but are potentially present, and that the ridges form something more than a nondescript congeries of ramifications and twists. He should continue to practise until he finds that the same ridges have been so nearly followed in duplicate impressions, that even in difficult cases his work will rarely vary more than a single ridge-interval.
When the triangular plot happens not to be visible, owing to the print failing to include it, which is often the case when the finger is not rolled, as is well shown in the prints of my own ten digits on the title-page, the trend of the ridges so far as they are seen, usually enables a practised eye to roughly estimate its true position. By means of this guidance an approximate, but fairly correct, outline can be drawn. When the habit of judging patterns by their outlines has become familiar, the eye will trace them for itself without caring to draw them, and will prefer an unoutlined pattern to work upon, but even then it is essential now and then to follow the outline with a fine point, say that of a penknife or a dry pen.
In selecting standard forms of patterns for the convenience of description, we must be content to disregard a great many of the more obvious characteristics. For instance, the size of generally similar patterns in Fig. 10 will be found to vary greatly, but the words large, medium, or small may be applied to any pattern, so there is no necessity to draw a standard outline for each size. Similarly as regards the inwards or outwards slope of patterns, it is needless to print here a separate standard outline for either slope, and equally unnecessary to print outlines in duplicate, with reversed titles, for the right and left hands respectively. The phrase "a simple spiral" conveys a well-defined general idea, but there are four concrete forms of it (see bottom row of Plate 11, Fig. 17, _oj_, _jo_, _ij_, _ji_) which admit of being verbally distinguished. Again the internal proportions of any pattern, say those of simple spirals, may vary greatly without affecting the fact of their being simple spirals. They may be wide or narrow at their mouths, they may be twisted up into a point (Plate 8, Fig. 14, ~52~), or they may run in broad curls of uniform width (Fig. 14, ~51~, ~54~). Perhaps the best general rule in selecting standard outlines, is to limit them to such as cannot be turned into any other by viewing them in an altered aspect, as upside down or from the back, or by magnifying or deforming them, whether it be through stretching, shrinking, or puckering any part of them. Subject to this general rule and to further and more particular descriptions, the sets (Plates 7 and 8, Figs. 11, 12, 13) will be found to give considerable help in naming the usual patterns.
It will be observed that they are grouped under the three principal heads of Arches, Loops, and Whorls, and that under each of these heads some analogous patterns as ~4~, ~5~, ~7~, ~8~, etc., are introduced and underlined with the word "see" so and so, and thus noted as really belonging to one of the other heads. This is done to indicate the character of the transitional cases that unite respectively the Arches with the Loops, the Arches with the Whorls, and the Loops with the Whorls. More will follow in respect to these. The "tented arch" (~3~) is extremely rare on the thumb; I do not remember ever to have seen it there, consequently it did not appear in the plate of patterns in the _Phil. Trans._ which referred to thumbs. On the other hand, the "banded duplex spiral" (~30~) is common in the thumb, but rare elsewhere. There are some compound patterns, especially the "spiral in loop" (~21~) and the "circlet in loop" (~22~), which are as much loops as whorls; but are reckoned as whorls. The "twinned loop" (~16~) is of more frequent occurrence than would be supposed from the examination of _dabbed_ impressions, as the only part of the outer loop then in view resembles outside arches; it is due to a double separation of the ridges (Plate 4, Fig. 8), and a consequent double interspace. The "crested loop" (~13~) may sometimes be regarded as an incipient form of a "duplex spiral" (~29~).
The reader may also refer to Plate 16, which contains what is there called the C set of standard patterns. They were arranged and used for a special purpose, as described in Chapter XI. They refer to impressions of the right hand.
As a variety of Cores, differing in shape and size, may be found within each of the outlines, it is advisable to describe them separately. Plate 8, Fig. 14 shows a series of the cores of loops, in which the innermost lineations may be either straight or curved back; in the one case they are here called rods (~31~ to ~35~); in the other (~36~ to ~42~), staples. The first of the ridges that envelops the core, whether the core be a rod, many rods, or a staple, is also shown and named (~43~ to ~48~). None of the descriptions are intended to apply to more than the _very end_ of the core, say, from the tip downwards to a distance equal to two average ridge-intervals in length. If more of the core be taken into account, the many varieties in their lower parts begin to make description confusing. In respect to the "parted" staples and envelopes, and those that are single-eyed, the description may further mention the side on which the parting or the eye occurs, whether it be the Inner or the Outer.
At the bottom of Fig. 14, ~49-54~, is given a series of rings, spirals, and plaits, in which nearly all the clearly distinguishable varieties are included, no regard being paid to the direction of the twist or to the number of turns. ~49~ is a set of concentric circles, ~50~ of ellipses: they are rarely so in a strict sense throughout the pattern, usually breaking away into a more or less spiriform arrangement as in ~51~. A curious optical effect is connected with the circular forms, which becomes almost annoying when many specimens are examined in succession. They seem to be cones standing bodily out from the paper. This singular appearance becomes still more marked when they are viewed with only one eye; no stereoscopic guidance then correcting the illusion of their being contour lines.
Another curious effect is seen in ~53~, which has the appearance of a plait or overlap; two systems of ridges that roll together, end bluntly, the end of the one system running right into a hollow curve of the other, and there stopping short; it seems, at the first glance, to run beneath it, as if it were a plait. This mode of ending forms a singular contrast to that shown in ~51~ and ~52~, where the ridges twist themselves into a point. ~54~ is a deep spiral, sometimes having a large core filled with upright and nearly parallel lines; occasionally they are bulbous, and resemble the commoner "monkey" type, see ~35~.
When the direction of twist is described, the language must be unambiguous: the following are the rules I adopt. The course of the ridge is always followed _towards_ the _centre_ of the pattern, and not away from it. Again, the direction of its course when so followed is specified at the place where it attains its _highest_ point, or that nearest to the finger-tip; its course at that point must needs be horizontal, and therefore directed either towards the inner or the outer side.
The amount of twist has a strong tendency to coincide with either one, two, three, four, or more half-turns, and not to stop short in intermediate positions. Here are indications of some unknown fundamental law, analogous apparently to that which causes Loops to be by far the commonest pattern.
* * * * *
The classification into Arches, Loops, and Whorls is based on the degree of curvature of the ridges, and enables almost any pattern to be sorted under one or other of those three heads. There are a few ambiguous patterns, and others which are nondescript, but the former are uncommon and the latter rare; as these exceptions give little real inconvenience, the classification works easily and well.
Arches are formed when the ridges run from one side to the other of the bulb of the digit without making any backward turn or twist. Loops, when there is a single backward turn, but no twist. Whorls, when there is a turn through at least one complete circle; they are also considered to include all duplex spirals.
The chief theoretical objection to this threefold system of classification lies in the existence of certain compound patterns, by far the most common of which are Whorls enclosed within Loops (Plates 7, 8, Fig. 12, ~15~, ~18~, ~19~, and Fig. 13, ~20-23~). They are as much Loops as Whorls, and properly ought to be relegated to a fourth class. I have not done so, but called them Whorls, for a practical reason which is cogent. In an imperfect impression, such as is made by merely dabbing the inked finger upon paper, the enveloping loop is often too incompletely printed to enable its existence to be surely ascertained, especially when the enclosed whorl is so large (Fig. 13, ~23~) that there are only one or two enveloping ridges to represent the loop. On the other hand, the whorled character of the core can hardly fail to be recognised. The practical difficulties lie almost wholly in rightly classifying a few transitional forms, diagrammatically and roughly expressed in Fig. 11, ~4~, ~5~, and Fig. 12, ~8~, ~18~, ~19~, with the words "see" so and so written below, and of which actual examples are given on an enlarged scale in Plates 9 and 10, Figs. 15 and 16. Here Fig. 15, _a_ is an undoubted arch, and _c_ an undoubted nascent loop; but _b_ is transitional between them, though nearer to a loop than an arch, _d_ may be thought transitional in the same way, but it has an incipient curl which becomes marked in _e_, while it has grown into a decided whorl in _f_; _d_ should also be compared with _j_, which is in some sense a stage towards _k_. _g_ is a nascent tented-arch, fully developed in _i_, where the pattern as a whole has a slight slope, but is otherwise fairly symmetrical. In _h_ there is some want of symmetry, and a tendency to the formation of a loop on the right side (refer back to Plate 7, Fig. 11, ~4~, and Fig. 12, ~12~); it is a transitional case between a tented arch and a loop, with most resemblance to the latter. Plate 10, Fig. 16 illustrates eyed patterns; here _l_ and _m_ are parts of decided loops; _p_, _q_, and _r_ are decided whorls, but _n_ is transitional, inclining towards a loop, and _o_ is transitional, inclining towards a whorl. _s_ is a nascent form of an invaded loop, and is nearly related to _l_; _t_ and _u_ are decidedly invaded loops.
The Arch-Loop-Whorl, or, more briefly, the A. L. W. system of classification, while in some degree artificial, is very serviceable for preliminary statistics, such as are needed to obtain a broad view of the distribution of the various patterns. A minute subdivision under numerous heads would necessitate a proportional and somewhat overwhelming amount of statistical labour. Fifty-four different standard varieties are by no means an extravagant number, but to treat fifty-four as thoroughly as three would require eighteen times as much material and labour. Effort is economised by obtaining broad results from a discussion of the A. L. W. classes, afterwards verifying or extending them by special inquiries into a few of the further subdivisions.
The divergent ridges that bound any simple pattern admit of nine, and only nine, distinct variations in the first part of their course. The bounding ridge that has attained the summit of any such pattern must have arrived either from the Inner plot (I), the Outer plot (O), or from both. Similarly as regards the bounding ridge that lies at the lowest point of the pattern. Any one of the three former events may occur in connection with any of the three latter events, so they afford in all 3 x 3, or nine possible combinations. It is convenient to distinguish them by easily intelligible symbols. Thus, let _i_ signify a bounding line which starts from the point I, whether it proceeds to the summit or to the base of the pattern; let _o_ be a line that similarly proceeds from O, and let _u_ be a line that unites the two plots I and O, either by summit or by base. Again, let two symbols be used, of which the first shall always refer to the summit, and the second to the base of the pattern. Then the nine possible cases are--_uu_, _ui_, _uo_; _iu_, _ii_, _io_; _ou_, _oi_, _oo_. The case of the arches is peculiar, but they may be fairly classed under the symbol _uu_.
This easy method of classification has much power. For example, the four possible kinds of simple spirals (see the 1st, 2nd, and the 5th and 6th diagrams in the lowest row of Plate 11, Fig. 17) are wholly determined by the letters _oj_, _jo_, _ij_, _ji_ respectively. The two forms of duplex spirals are similarly determined by _oi_ and _io_ (see 4th and 5th diagrams in the upper row of Fig. 17), the two slopes of loops by _oo_ and _ii_ (3rd and 4th in the lower row). It also shows very distinctly the sources whence the streams of ridges proceed that feed the pattern, which itself affords another basis for classification. The resource against uncertainty in respect to ambiguous or difficult patterns is to compile a dictionary of them, with the heads under which it is advisable that they should severally be classed. It would load these pages too heavily to give such a dictionary here. Moreover, it ought to be revised by many experienced eyes, and the time is hardly ripe for this; when it is, it would be no difficult task, out of the large number of prints of separate fingers which for instance I possess (some 15,000), to make an adequate selection, to enlarge them photographically, and finally to print the results in pairs, the one untouched, the other outlined and classified.
It may be asked why ridges are followed and not furrows, the furrow being the real boundary between two systems. The reply is, that the ridges are the easiest to trace; and, as the error through following the ridges cannot exceed one-half of a ridge-interval, I have been content to disregard it. I began by tracing furrows, but preferred the ridges after trial.
_Measurements._--It has been already shown that when both plots are present (Plate 4, Fig. 8, ~4~), they form the termini of a base line, from which any part of the pattern may be triangulated, as surveyors would say. Also, that when only one plot exists (~3~), and the pattern has an axis (which it necessarily has in all ordinary _ii_ and _oo_ cases), a perpendicular can be let fall upon that axis, whose intersection with it will serve as a second point of reference. But our methods must not be too refined. The centres of the plots are not determinable with real exactness, and repeated prints from so soft a substance as flesh are often somewhat dissimilar, the one being more or less broadened out than the other, owing to unequal pressure. It is therefore well to use such other more convenient points of reference as the particular pattern may present. In loops, the intersection of the axis with the summit of the innermost bend, whether it be a staple or the envelope to a rod (Fig. 14, second and third rows of diagrams), is a well-defined position. In spirals, the centre of the pattern is fairly well defined; also a perpendicular erected from the middle of the base to the outline above and below (Fig. 8, ~4~) is precise and convenient.
In prints of adults, measurements may be made in absolute units of length, as in fractions of an inch, or else in millimetres. An average ridge-interval makes, however, a better unit, being independent of growth; it is strictly necessary to adopt it in prints made by children, if present measurements are hereafter to be compared with future ones. The simplest plan of determining and employing this unit is to count the number of ridges to the nearest half-ridge, within the space of one-tenth of an inch, measured along the axis of the finger at and about the point where it cuts the _summit_ of the outline; then, having already prepared scales suitable for the various likely numbers, to make the measurements with the appropriate scale. Thus, if five ridges were crossed by the axis at that part, in the space of one-tenth of an inch, each unit of the scale to be used would be one-fiftieth of an inch; if there were four ridges, each unit of the scale would be one-fortieth of an inch; if six ridges one-sixtieth, and so forth. There is no theoretical or practical difficulty, only rough indications being required.
It is unnecessary to describe in detail how the bearings of any point may be expressed after the fashion of compass bearings, the direction I-O taking the place of East-West, the uppermost direction that of North, and the lowermost of South. Little more is practically wanted than to be able to describe roughly the position of some remarkable feature in the print, as of an island or an enclosure. A ridge that is characterised by these or any other marked peculiarity is easily identified by the above means, and it thereupon serves as an exact basis for the description of other features.
_Purkenje's "Commentatio."_
Reference has already been made to Purkenje, who has the honour of being the person who first described the inner scrolls (as distinguished from the outlines of the patterns) formed by the ridges. He did so in a University Thesis delivered at Breslau in 1823, entitled _Commentatio de examine physiologico organi visus et systematis cutanei_ (a physiological examination of the visual organ and of the cutaneous system). The thesis is an ill-printed small 8vo pamphlet of fifty-eight pages, written in a form of Latin that is difficult to translate accurately into free English. It is, however, of great historical interest and reputation, having been referred to by nearly all subsequent writers, some of whom there is reason to suspect never saw it, but contented themselves with quoting a very small portion at second-hand. No copy of the pamphlet existed in any public medical library in England, nor in any private one so far as I could learn; neither could I get a sight of it at some important continental libraries. One copy was known of it in America. The very zealous Librarian of the Royal College of Surgeons was so good as to take much pains at my instance, to procure one: his zeal was happily and unexpectedly rewarded by success, and the copy is now securely lodged in the library of the College.
_The Title_
Commentatio de Examine physiologico organi visus et systematis cutanei quam pro loco in gratioso medicorum ordine rite obtinendo die Dec. 22, 1823. H.X.L.C. publice defendit Johannes Evangelista Purkenje, Med. doctor, Phys. et Path. Professor publicus ordinarius des. Assumto socio Guilielmo Kraus Medicinae studioso.
_Translation_, p. 42.
"Our attention is next engaged by the wonderful arrangement and curving of the minute furrows connected with the organ of touch[4] on the inner surfaces of the hand and foot, especially on the last phalanx of each finger. Some general account of them is always to be found in every manual of physiology and anatomy, but in an organ of such importance as the human hand, used as it is for very varied movements, and especially serviceable to the sense of touch, no research, however minute, can fail in yielding some gratifying addition to our knowledge of that organ. After numberless observations, I have thus far met with nine principal varieties of curvature according to which the tactile furrows are disposed upon the inner surface of the last phalanx of the fingers. I will describe them concisely, and refer to the diagrams for further explanation (see Plate 12, Fig. 19).
1. _Transverse flexures._--The minute furrows starting from the bend of the joint, run from one side of the phalanx to the other; at first transversely in nearly straight lines, then by degrees they become more and more curved towards the middle, until at last they are bent into arches that are almost concentric with the circumference of the finger.
2. _Central Longitudinal Stria._--This configuration is nearly the same as in 1, the only difference being that a perpendicular stria is enclosed within the transverse furrows, as if it were a nucleus.
3. _Oblique Stria._--A solitary line runs from one or other of the two sides of the finger, passing obliquely between the transverse curves in 1, and ending near the middle.
4. _Oblique Sinus._--If this oblique line recurves towards the side from which it started, and is accompanied by several others, all recurved in the same way, the result is an oblique sinus, more or less upright, or horizontal, as the case may be. A junction at its base, of minute lines proceeding from either of its sides, forms a triangle. This distribution of the furrows, in which an oblique sinus is found, is by far the most common, and it may be considered as a special characteristic of man; the furrows that are packed in longitudinal rows are, on the other hand, peculiar to monkeys. The vertex of the oblique sinus is generally inclined towards the radial side of the hand, but it must be observed that the contrary is more frequently the case in the fore-finger, the vertex there tending towards the ulnar side. Scarcely any other configuration is to be found on the toes. The ring finger, too, is often marked with one of the more intricate kinds of pattern, while the remaining fingers have either the oblique sinus or one of the other simpler forms.
5. _Almond._--Here the oblique sinus, as already described, encloses an almond-shaped figure, blunt above, pointed below, and formed of concentric furrows.
6. _Spiral._--When the transverse flexures described in 1 do not pass gradually from straight lines into curves, but assume that form suddenly with a more rapid divergence, a semicircular space is necessarily created, which stands upon the straight and horizontal lines below, as it were upon a base. This space is filled by a spiral either of a simple or composite form. The term 'simple' spiral is to be understood in the usual geometric sense. I call the spiral 'composite' when it is made up of several lines proceeding from the same centre, or of lines branching at intervals and twisted upon themselves. At either side, where the spiral is contiguous to the place at which the straight and curved lines begin to diverge, in order to enclose it, two triangles are formed, just like the single one that is formed at the side of the oblique sinus.
7. _Ellipse_, or _Elliptical Whorl_.--The semicircular space described in 6 is here filled with concentric ellipses enclosing a short single line in their middle.
8. _Circle_, or _Circular Whorl_.--Here a single point takes the place of the short line mentioned in 7. It is surrounded by a number of concentric circles reaching to the ridges that bound the semicircular space.
9. _Double Whorl._--One portion of the transverse lines runs forward with a bend and recurves upon itself with a half turn, and is embraced by another portion which proceeds from the other side in the same way. This produces a doubly twisted figure which is rarely met with except on the thumb, fore, and ring fingers. The ends of the curved portions may be variously inclined; they may be nearly perpendicular, of various degrees of obliquity, or nearly horizontal.
In all of the forms 6, 7, 8, and 9, triangles may be seen at the points where the divergence begins between the transverse and the arched lines, and at both sides. On the remaining phalanges, the transverse lines proceed diagonally, and are straight or only slightly curved."
(He then proceeds to speak of the palm of the hand in men and in monkeys.)