Kitabı oku: «Dactylography», sayfa 2

CHAPTER II
SWEAT-PORES, RIDGES AND FURROWS

Section of Skin, showing Sweat-Glands, Ducts and Pores

a. pore open.

b. pore closed.

d. sweat duct.

e. sweat gland.

The front or palmar surface of human hands, and the corresponding solar or plantar surface of the feet, are marked with alternate ridges and furrows, lying for the most in nearly parallel rows, but often again at certain points on palm or sole, curving, splitting, twisting, or joining to form patterns of much intricacy. The ridges, called technically rugæ (sing. ruga), are punctuated at very frequent intervals with small openings, which are the mouths or pores of the sweat ducts connected with certain glands which lie deep in the lower strata of the skin. The furrows or sulci (sing. sulcus) are almost devoid of any such apertures. There are probably some two or three millions of those tiny sweat pores in a human body, which afford an evaporating surface, according to the anatomist Krause, of about eight square inches. The sweat is a watery, slightly saline fluid, with slight – very slight – traces of grease, some small cell-like particles, and some carbonic acid and other gaseous matters, which exhale from the skin. The more oily secretion of the skin comes from a different set of openings with their associated glands, the sebaceous glands, which are associated with the hairy surfaces of the body. In Ludwig Hopf’s work, The Human Species, the subject is discussed fully. When the palmar surface leaves a distinctly greasy impression, this greasiness must have been acquired from outside or from transmitted exudation from the back or dorsal surfaces, or other parts of the body.

Those skin ridges, apart from any relation they may have either to the sweat-pores or to the special nerves of touch and temperature which lie near them, serve a useful purpose in helping the horny hands of toil to grasp its tools firmly. They occur in a few other parts of animals somewhat near to us in the scale of being. A striking example is that on the palmar surface of the prehensile or grasping tail of the Spider Monkey (Ateles ater), which it uses in climbing almost like a hand.

When the ridges in human fingers are well softened with water, and are then rubbed along the surface of a tumbler or wine-glass, musical sounds may be elicited, which are caused by the alternate resistance and yielding of the softened ridges. This was the principle of the “musical glasses” of Goldsmith’s time. The navvy often begins his labours by moistening his loof. After his efforts make him perspire, he has no further need in this way for his salivary resources. Hence Nature, too, has placed the openings of the sweat-pores on the crests of his ridges, and not, as Herbert Spencer on one occasion is said to have supposed she had done, in the troughs of the furrows, where they are very seldom to be found, and would not be nearly so useful. Curiously enough, our modern makers of indiarubber tyres work a trademark pattern or title in ridges on their wares, so as to secure a good grip on the road – and on the market. In a similar way the carriers of Manchuria adorn their clumsy wheels with studs to prevent their skidding.

There are, as has been mentioned, two kinds of minute glands in the skin: one, to secrete that complex excretion, the sweat; the other, to provide a certain greasiness to hair. The latter are found chiefly in other parts than the palms, and serve to secure that slight oiliness of the surface of our bodies which is very well seen in taking one’s bath. However thoroughly that thin film of surface greasiness is removed with the use of soap and vigorous scrubbing, in a moment or two water is seen to act on the cutaneous surface as it would on a slightly greasy platter or a duck’s back. The importance of this point will become apparent when we come to deal with some practical applications of dactylography in searching for invisible greasy finger-marks, which may be made visible.

Looking carefully at the visible texture of the fingers and palms, we see, then, that the cutaneous ridges lie, for the most part, closely and evenly, like furrows in a well-ploughed field. But just as in some fields the ploughman has perforce had to swerve and veer round some fast embedded boulder or old tree stump, varying his intended pattern, so, too, in our fingers curious divergent lineations are found to occur, and we cannot very well tell the reason why. Coloured patches may be designed like so many pretty wall-paper designs, to enclose these patterns in books on finger-prints, but I, for one, cannot see that they throw any light on their genuine nature and origin. We find, under purely mechanical conditions, similar patterns produced in the ripples of a sub-aerial sand-drift and on a tidal shore. While writing this chapter, I saw to-day similar deltas, junctions, forks, and the like, on a lake whose frozen surface was thinly sprinkled with fine dry snow. The lines were mostly parallel, but where certain gusts or eddies had occurred they had been broken up into patterns not unlike those of finger-tips.

Ripple Marks in Sand (After Lyell).

In human skin, and in the anthropoid apes, those scroll-like patterns present almost infinite varieties of detail, and they often resemble a condensed railway plan, showing junctions, blind sidings, loops, triangles, and curves. There is one important distinction to be observed. The lineations of skin ridges are not always quite uniform in breadth, but broaden out sometimes or dwindle away. Again, they are dotted with sweat-pores and do not always, when printed from, show those pores in the same degree of patency or openness. Hence a little variation is inevitable when the same finger is several times impressed under varying conditions. It is not to be forgotten that, to a limited extent, this is true of a rigid box-wood engraving or steel plate, or lithographic stone, which give somewhat divergent results with varying degrees of pressure in printing, moisture of atmosphere or paper, and other conditions.

In this country the feet do not afford a favourable field of study to the dactylographer. So far as identification is concerned, little use could be made of them practically. In the East, however, it is different, and many years’ residence there gave me opportunities to observe that the toes, unrestrained by the use of stiff leather boots, are mobile and powerful, grasping as fingers do. The carpenter in Japan, for example, uses his toes to grip and steady the board he is sawing or hewing, while many of my readers must be familiar with the extraordinary agility of Japanese acrobats in the use of their feet and toes. In those cases the ridges are often varied in grouping, and well defined in development. A European baby generally begins life with similar simian-like powers. But so far as my own observations go, the patterns in the hands usually show a somewhat higher degree of evolution, a more complex and intricate network of lines, than those exhibited by the feet of the same person. Hence, apart from the greater convenience of inspecting them, the finger-prints have greater value for the purpose of identification. Cases, however, of crime, might readily occur even in this country, where the imprints of naked feet might yield important and irrefutable evidence of one’s presence at a scene of evil-doing.

But there are other important points of scientific interest besides their evidential value for identification. An important problem in evolutionary development, on which a considerable amount of literature begins to accumulate, is the serial relation of the limbs. Professor Bowditch, the distinguished biologist, of Harvard University, U.S., wrote me, of date November 18th, 1880, thus: —

“Dear Sir, – I have just read in Nature of October 28th, your article on the skin-furrows of the hand. The subject interested me because it so happened that fourteen years ago, at the suggestion of the late Professor Jeffries Wyman, I made some prints of the finger and toe tips with the hope of throwing some light on the question of the antero-posterior symmetry of the body. Since reading your article I have made some new impressions from the same individual, and it is interesting to notice the unchanged character of the cutaneous furrows.”

Some additional particulars are added in the letter, and a fine finger imprint was enclosed.

It is well to remember that the comparison of the ridges to those of a ploughed field does not always, and in every way, hold good. As I have elsewhere said:[C]

“The lines are not of uniform width. Ofttimes they may be likened rather to the mountains and valleys in a good survey. The ridges sometimes split or send little spurs down into the neighbouring valleys; at other times a ridge seems to cleave, giving rise to a form like a tarn or lake in a limestone range: here and there solitary islands rise in the valleys, and sometimes quite an archipelago takes the place of some of the commoner patterns. Indeed, the ordinary nomenclature of an ordinary physical geography map may be found quite helpful in laying a case clearly before a magistrate or a jury. And just as we find in the case of mountains and valleys in a map, every variety of shape may occur in a finger-pattern.”

Here it may be as well to state, as we shall see more precisely further on, that an English jury is well enabled to judge of the conformity of two patterns, one of which is suspect only, and the other officially printed from the fingers of some one in custody – by great photographic enlargement of the exhibits in the case, used as evidence.

The ridges, as may be seen by an enlarged photograph (as on frontispiece), do not always continue to be of quite uniform width throughout. Sometimes they taper away sharply like a railway point, or trickle off in diminishing dots; or again, especially where something like triangles occur, called deltas (after the Greek letter, Δ delta), they flatten out in breadth considerably. In old age they are found usually to have partaken of the general drying up and shrivelling of the tissues.

In the cold or shivering stage of ague and fevers, and in the affection called Reynaud’s disease, in which the fingers may tend to become pale and bloodless, some slight shrinking of the ridges also takes place, a point which might be of importance in the measurement of enlarged exhibits in the trial, for example, of an old Indian soldier or traveller who had been subject to fits of ague.

I have heard Sir A. Moseley Channel, who has informed himself well about finger-print matters, in a charge to a jury in a murder case, refer to the doubtful and unsatisfactory nature of evidence from a print done by a sweaty finger.

The fact that sweaty finger-marks have been adduced in evidence of crime makes it important for lawyers, police officials, judges and jurymen, to understand what is meant by such natural records. A mark from pure sweat would necessarily be excessively transient, as it consists chiefly of water and salines, and should properly contain no greasy matter whatever. Dr. Reginald Alcock, of the North Stafford Infirmary, in a recent paper read at Stoke-on-Trent, and since republished in The British Medical Journal, described his researches into the relation of the sweat-pores to practical surgery, and to the recognized difficulty in sterilising the skin for subsequent operation. Dr. Alcock shows that there may often be found remaining, after the best efforts to cleanse the surface, a stubborn residue of live and obnoxious matter in those tiny invisible ducts, matter which had insidiously gained entrance from without. Now such decaying or dead particles of foreign protoplasm would, I think, readily enough account for the very faint traces of oily matter sometimes observed, which oiliness makes sweat from a skin, fair and clean in the ordinary sense, leave slight but somewhat persistent traces on such substances as glass and the like.

In a case reported some time ago, in The Birmingham Post, Detective-Sergeant Charles Munro, on cross-examination as to a sweaty smudge left on glass, said: “The impressions on the window-pane were sweat-marks. They had conducted experiments in Scotland Yard, and ascertained that sweat-marks lasted on glass for a week if not exposed to the wind.” Here, I suppose, the distinction between a sweat-mark proper and a somewhat greasy sweat-mark was not discerned. Even a deliberately designed greasy mark is volatile to a certain extent just as the oil of new paint dries in a day or two according to the weather.

In the Guide (p. 65) I have alluded to the fact of coloured sweat or Chromidrosis, thus: —

“A blackish ooze takes place in some hysterical cases. More striking is the class of cases in which the colouring matter is derived, like the bright colours in the plumage of parrots, from copper, and in some cases from iron. Workers in copper have been found subject to it. The sweat is generally of a bluish colour in those cases. Red sweat has been observed in lockjaw. A kind of saffron colour I have found to be not very uncommon in some classes of malarious cases. One lady I attended had an extraordinary temperature during some of the attacks, the thermometer recording 110° Fahrenheit. With a temperature of about 104° Fahr. she did not seem to be really unwell. I took good impressions at one of those times, with the yellow-coloured sweat. Ordinarily, however, sweat does not help, but hinder, impressions from being made. A case of blue sweat came under my treatment quite recently. There was no history of copper poisoning.”

Since writing the above, I have met with other cases of coloured sweat. My teacher, the late Sir Thomas McCall Anderson, in his work, Contributions to Clinical Medicine, mentions some very interesting facts in this connection in the chapter on “Hemidrosis.”

Herbert Spencer, in the May number of the Nineteenth Century (1886), discussing the Factors of Organic Evolution, explains the origin of the ridges in a passage which I must quote in full: —

“Continuous pressure on any portion of the surface causes absorption, while intermittent pressure causes growth: the one impeding circulation and the passage of plasma from the capillaries into the tissues, and the other aiding both. There are yet further mechanically produced effects. That the general character of the ribbed skin on the under-surfaces of the feet and inside of the hands, is directly due to friction and intermitten pressure, we have the proofs: first, that the tracks most exposed to rough usage are the most ribbed; second, that the insides of hands subject to unusual amounts of rough usage, as those of sailors, are strongly ribbed all over; and third, that in hands which are very little used, the parts commonly ribbed become quite smooth.”

CHAPTER III
FINGER-PRINT PATTERNS

Before reading this chapter, let the reader carefully examine the clear lineations shown so well in the photographic picture of the Zebra’s stripes, opposite. They will be found to resemble very closely the lineations on the skin of human fingers, as printed when enlarged by photography, forming very similar patterns. Similar linings occur in the hide of the tiger.

Grevy’s Zebra. – Showing Lineations like Finger-Print Patterns.

[Photo. Pictorial Agency]

Where two lines, beginning as parallels, curve to divide, a fresh line begins to appear between. Sometimes a single line forks into two or three. Again, triangular arrangements of lineations are seen on the zebra, and one can trace some of these back into lines running as a parallel series. Surely the causes which produce the ridges on a human or anthropoid finger cannot be quite the same biologically as lead to the formation of similar patterns in the skin of the zebra. There are mechanical or physical conditions, however, which condition the formation of ridges in a sandy shore, of powdery snow blown by the wind and tossed on a smooth frozen lake, as has already been noticed, and these conditions are being carefully elucidated by scientific observers. But why living tissues should produce patterns like those, just in those positions, and then reproduce them in living descendants with slight but important variations, is a totally different question, the answer to which must be reached in a different way.

While the ridges and furrows lie in parallels or curve in the same direction over some considerable surface of the sole and palm, they also gather up into more or less intricate, scroll-like patterns at various points besides those of the last joints of the fingers, which have chiefly engrossed popular attention hitherto. In man, the lemurs, lemuroids, and apes, these pattern points are numerous. In my own hands, there are on the left hand, besides the five finger-tip patterns, other five like them, and the right hand contains six. There are thus twenty-one complex patterns which might be used for identification.

On the other hand, when one reads of a mathematical attempt to compute the probabilities of two finger-prints being alike, it is not a question simply of comparing an unknown finger smudge with collections containing ten finger-prints each, for the unknown smudge may have been made, not from one of a possible set of ten finger-tip prints, but from one of those other local patterns not on the finger-tips at all. There is a saying often attributed to Huxley, who certainly used it wisely, that the value of grist from the mathematical mill depends on the quality of the corn put into the hopper. But official amateur mathematicians have made many much worse mistakes than the above in regard to probabilities in the realm of finger-print evidence.

In a few cases, especially in the feet patterns, often a very plain character, parallel or slightly wavy lines of no precise design, so to speak, may be found. A short time ago, when applying mustard to the feet of a lady in some kind of fit, I observed this almost featureless pattern in her toes. If such cases were as common in the hands as they are rare, the finger-print method would hardly be of any avail for identification. A teleologist of the old school of Paley might argue with some plausibility that the possible usefulness of those intricate patterns was the true meaning of their existence, otherwise not yet explainable. That the old Paleyan conception of nature having an end or purpose in view, the teleological explanation of things as useful to the being possessing them, had its own usefulness in giving a broader view of natural history facts in their interrelations, is borne out even by so great an authority as Charles Darwin himself. Are the markings in a bird’s eggs recognized by the sitting bird in those cases where the markings are peculiar – and some are like written characters – or are they purely accidental and useless? A correspondent in The Country-Side wrote a short time ago, describing a test case he observed of a thrush in his possession. This bird built a nest and laid therein five eggs, “varying in size from a good-sized pea to the normal size. The smaller ones I took away and substituted one from a wild bird’s nest; this the following day I found laid at the bottom of the aviary smashed. I again repeated the addition with the same result. I had carefully marked the eggs, so that there could be no mistake.” The writer signed himself “W. A., Wimbledon.”

Dr. Wallace’s view, as I understand it, is that variations in wild animals were due chiefly to immunity from enemies, allowing free play to the natural tendency to variation, kept only in check by its dangers, such as leading to betrayal by conspicuous colouring, and so on. Professor Poulton in The Colours of Animals, 2nd ed. p. 212, says: —

“It is very probable that the great variation in the colours and markings of birds’ eggs, which are laid close together in immense numbers, may possess this significance, enabling each bird to know its own eggs. I owe this suggestive interpretation to my friend, Mr. Francis Gotch: it is greatly to be hoped that experimental confirmation may be forthcoming. The suggestion could be easily tested by altering the position of the eggs and modifying their appearance by painting. Mr. Gotch’s hypothesis was formed after seeing a large number of eggs of the guillemot in their natural surroundings.”

Australian ewes know the bleat of their own lambs, however immense the flock, and all through nature we find this useful note of recognition. One of the most philosophic interpreters of living phenomena, viewing things from a very recent standpoint – Professor J. Arthur Thomson, in his fascinating Biology of the Seasons (p. 174), writing of the colour and texture of birds’ eggs, says: —

“In some cases, it is said, the shell registers hybridism – a very remarkable fact. It is another illustration of the great, though still vague, truth that the living creature is a unity through and through, specific even in the structure of the egg-shell within which it is developed. For although the shell is secreted by the walls of the oviduct, it seems to be in some measure controlled by the life of the giant-cell – the ovum – within.”

Such pattern-forming qualities are found in many fields of nature, very beautifully, for example, as we have seen, in the skin of the zebra; on the back of a mackerel; in the grain of various kinds of wood; in the veining of leaves and petals; and in the covering or substance of seeds such as the nutmeg and scarlet runner bean. Sir Charles Lyell, in his Elements of Geology, figures the ribbing of sand on the sea-shore in a wood-cut which might be an enlarged diagram of human skin. (See fig. on page 32). In his Principles of Geology (5th ed., vol. i., p. 323) there is, again, a figure described as a section of “spheroidal concretionary Travertine,” which contains many linings strikingly like those with which we have to deal in this little work.

a. section of pine-wood stem.

b. a human thumb-print.

It follows from these analogies that a method of analysing and classifying such patterns might have very wide utilities beyond its relation to finger-prints. It is easy, for example, to recognize the same zebra in quite different pictures. Another point of practical importance is this, that a smudgy or blotchy impression, supposed to be that of a criminal present at some seat of crime, might be the impressed copy merely of some object or texture other than human skin, but containing lineations of similar arrangement. An outworn transversely cut branch of a tree might readily produce a print like that of a human finger. An expert would probably notice that in the lineations there were no real junctions, each woody ring remaining apart from the others; but, again, there are some human fingers of such patterns. I think the bloody smear officially reproduced as impressed on a post-card in facsimile, and purporting to have come from “Jack the Ripper,” at the time of the Whitechapel horrors in the eighties, may have been produced by the sleeve of a twilled coat smeared with blood. It contained no characters specially characteristic of skin lineations, which it was presumed to be an example of, as impressed.

Apart from all that, lemurs, lemuroids, apes, anthropoids, and monkeys, all show on hands and feet, skin lineations in patterns similar to those of man. In the anthropoid apes it would not be easy to discriminate them from those of human beings. Some of these were figured in my Guide, and Dr. Otto Schlaginhaufen has supplied numerous good prints.

If Edgar A. Poe, in his famous mystery of evil deeds done by a gigantic ape, had been acquainted with finger-print methods, he might have pictured the police as still more mystified by the imprints of seemingly human hands.

There are two methods of observing systematically the lineation patterns.

1. —The Direct Mode.– This might be done simply by many people by looking at the lineations with the unaided vision. Till quite recently the author found no difficulty in doing this, with myopic eyes that could see something of the texture of a house-fly’s eyes in a good light. My earliest observations of the finger-patterns were made in this way, while the patterns were reproduced in pencilled outlines. The condition of the actual ridges and furrows themselves, with their open and acting or closed and dormant sweat-pores, ought to be familiar to the student of dactylography, who is apt to narrow his vision by the contemplation only of dead impressions made in ink or otherwise. A lens such as botanists use for field work is very useful, and a high power is neither necessary nor very helpful. Drawings of the patterns ought to be made from time to time with coloured or “lead” pencils, and those drawings should be accurately adjusted by the use of rubber and compasses.

2. —The Indirect Method.– This is done by the medium of casts and printed impressions. Casts may be made of clay, putty, sealing-wax, beeswax, gutta-percha, hard paraffin, varnish, half-dry paint, and the like. Printed impressions or dactylographs may be obtained from greasy or sweaty fingers, blood, printer’s ink, or various substitutes for it.

Within this method, again, two very distinct and complementary kinds of results may be obtained, which I have elsewhere described as Positive and Negative. The first or Positive is that, for example, which is used officially for the record of convicted prisoners by printing with ordinary printer’s ink, just as a veined leaf or fern, or a box-wood engraving is printed from. Here the ridges or raised lines appear black on a white ground, while the intervening furrows appear white, as do also the minute pores dotted along the crest of each ridge. (See frontispiece.)

In the other method, as when the fingers are impressed on a carefully smoked surface of glass, the projecting ridges lift up the carbon of the soot, leaving a white pattern behind, with the sweat-pores forming black punctuations, while the receding furrows leave the black surface untouched. When such impressions have to be used again, as for evidence, they should be carefully varnished, as they are exceedingly liable to be destroyed by the slightest contact.

In a case under judicial investigation where an official imprint had to be compared with one done by accident negatively on smoked glass or the like, the black lineations would not closely correspond – would, in fact, considerably diverge in pattern. This might tend to confuse judge and jury if the distinction of negative and positive dactylograph were not made clear by the expert witness. Then the apparent divergences could easily be demonstrated to be very significant coincidences.

Five years of my early life were spent in learning a trade in Glasgow – that of the soon-to-be-obsolete Paisley shawl manufacture. It seemed to me to have been an utter waste of time, but part of my duty was to deal with the arrangement, classifying, and numbering immense varieties of patterns, printed with every conceivable variation of combined colours. It was impossible to carry these on memory, and one had to resort to mnemonic means of classification.

Now, the immense significance of the variety in human finger-patterns dawned upon me very early, when I had once begun to interest myself in them.

Design-like Patterns in Finger-Prints No. 1.

(Diagrammatic)

Design-like Patterns No. 2.

There are many patterns, which, when analysed into their composing elements, present analogies to artistic designs, a view which is no mere personal fad, but has been affirmed with enthusiasm by many artists in designs to whom I have pointed out those figures. Here are a few, by way of illustrating this point (space will not permit of more). Those figures are from real human finger-prints rendered diagrammatically. This is the first step, then, to catch with the eye the pattern or design; give it a class name, and you have at once established some practical basis of classification in finger-prints. Then it is possible to frame some kind of catalogue for reference arranged like a dictionary with its sub-alphabetic order, in an almost infinite series. The initial difficulty is generally that which arises from want of skill in printing, which technical points will be considered subsequently. A soft and flexible substance like the ridges in human fingers does not always yield an exactly similar impression in two successive moments, under varying conditions of temperature, fatigue, and the like. Nor does the analogy of mathematical diagrams always fitly apply in such a case. Even in steel engravings and fine etchings, as the connoisseur well knows, the degree of intensity of the pressure and other conditions will modify to some slight extent the resulting imprint, but what I wish to emphasize is, that if the original pattern had any value at all resulting from its complexity as a pattern, the variation in printing as now done officially by experienced police officials will not impair much its value as evidence of personal identity in a court of law. Even the amateur will soon, after a little practice with good materials, attain a very fair amount of clearness and uniformity in his imprints.