Thus if, as shown above, a set of formulæ would be divided into upwards of 50 divisions by using the left hand alone, and if each of these would be farther subdivided by adding the formulæ of the right hand, producing 2,500 divisions in all, the addition of the left foot to these might increase the number to 2,500 X 50, or 125,000, and these would become 7,250,000 by the use of the right foot, or enough to characterize every citizen in a large state or small country, employing merely the primary classification. It must be remembered, however, that these are theoretical figures and that the actual combinations of lines may not be as great, nor would the various kinds be as regularly distributed; yet enough has been shown to prove that the number of separate actual combinations of the line formulæ alone, if both the hands and feet are employed, would be very great.
In a sole print the characteristic features are mainly distributed along the ball of the foot, anterior to the hollow of the arch, and while in a general way they are similar to those of the hand, there are also numerous important differences, some of which will be seen in Fig. 5, a print which represents a more complex condition than is usually seen, and in the tracings given in Fig. 6. The four main lines of the sole, although arising from digital triradii, usually curve towards the inner instead of the outer side, and when open, are apt to converge at the inner margin almost or quite to the point of fusion. There is also almost always upon the thenar region or ball of the great toe a conspicuous pattern, which may be termed the hallucal pattern. This possesses one or two, and possibly three triradii, of which the upper one is the proper digital triradius of the great toe, usually unrepresented in the hand; while there is often a second one upon the extreme inner margin, sometimes shown only by rolling the foot a little during printing. The hallucal pattern shows much variation and is easily divisible into a series of types, which well serve the purpose of a secondary classification. Lower triradii are of far more frequent occurrence than in the hand, and are often located so near one another through the convergence of the interdigital areas that it is difficult or impossible to attribute them to any one of them.
Probably the greatest barrier to the formulation of sole conditions in the same way as in the case of the palms lies in the position of the digital triradii, which are apt to be situated in the hollow beneath the toes and thus beyond the margin of a print—a condition especially apt to occur in the case of the third one, i. e., that at the base of the fourth toe; again, the relationships of the triradii are often complicated by the fusion of two or more digital areas with one another and the consequent displacement of the digital lines, which may simply pass one another upon the digital areas or curve downwards over the ball of the foot as
