“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.”