This section is from the book "The Laws Of Scientific Hand Reading", by William G. Benham. Also available from Amazon: The Laws of Scientific Hand Reading.
UPON entering our bodies through the finger of Jupiter the first line reached by the Electric Current is the line of Heart, so named because it has been found to reflect accurately the condition and operation of this organ. It is a very important line, as it deals with that central life-sustaining mechanism which pumps and controls the blood stream, which, by its quantity and quality, we have found so largely affects our health and temperament. The line of Heart rises from some point under or near the finger of Jupiter, and traces its way across the hand under the Mounts, ending on the percussion. It is not proper to say that this line has any normal starting place, or any normal stopping place, for what might be normal with one subject would not be with another, so the line of Heart must always be considered in relation to the individual on which it is seen. The old saying, that a person has a "warm heart" or a "great deal of heart," has become synonymous with the idea that these persons are affectionate and sympathetic. This is largely true, for we have already seen that the action of a strong heart is followed by pink color, indicating warmth and health, and this we know produces genial, sympathetic people.
Plenty of blood, pumped by a strong heart, means the antithesis of whiteness and coldness. So a "warm heart" really refers to the physical health of that organ, and the warmth that follows good blood supply, which condition produces the consequent attraction towards its fellow-men peculiar to such natures. Thus we find that a strong physical heart means not only health, but a strong attraction for and to others. And, conversely, a weak, flabby heart, pumping the blood current with lifeless force, produces white color, which indicates a lack of warmth, and consequent weak or less magnetic or energetic quality of affections. Those to whom the reading of variations in the affections from the Heart line has seemed impossible have not recognized the direct connection existing between the strength of the physical organ and the emotions, for every variation in the strength of the heart's action produces more or less health and a corresponding variation in the kind and strength of the affections. Thus the Heart line is, in truth, a revealer not only of the muscular, vital strength and action of the heart itself, but, as a result of these conditions, also of the strength and character of the affections.
You will not find the line of Heart absent in many hands, and yet it sometimes is. You will occasionally see only one line crossing the hand below the Mounts, and will be at a loss to tell whether it is the Head or Heart line. I have but once seen the Head line entirely absent, though I have seen many hands lacking the Heart line. (I had intended at this point to show this hand with Head line absent, but upon going to secure a print, found that a Head line had appeared in the hand since I last saw it, a period of about a year.) If we consider that the lines are controlled by the brain, and not by the heart, we can understand that the Head line will nearly always be present, being the indicator of that organ which controls and produces all lines. It is often seen, however, in a very elementary state of development. When a single line is seen occupying a position which is, relatively, where the Head line ought to be, it should be classed as a Head line and the Heart line considered to be absent. In order that this single line may be considered the Heart line and not the Head line, it must rise high on the Mount of Jupiter (24), or in that vicinity, and must trace its way across the hand just under the Mounts, and not by any means low enough to be in the location of the Head line.
When the Heart line is absent, its absence speaks of a lack of sympathy and the affectionate side of the disposition, and warns us of one who is coldblooded, selfish, and who desires personal success even at the expense and detriment of others. It is a bad marking, which easily leads from mere selfishness into hypocrisy, deceit, lack of candor, and positive dishonesty.

No. 24.
If this marking is seen in the hand of a bad Mercurian, or even of an unusually shrewd specimen of this type, it will at once mean natural temptation toward dishonesty. If the finger of Mercury is crooked and twisted, and the nails are narrow or short, you may be sure that the subject cannot be trusted. He will lie, swindle, cheat, steal, or do anything to get money; this is the hand of typical cold-blooded dishonesty. On a Martian the absence of the Heart line would show him to be unscrupulous, cold-blooded, and even on provocation bloodthirsty and dangerous. He will burn with physical ardor, and will gratify his lusts with no thought of the consequences to his victim. On a Saturnian it is a distressing indication, for it will add to his natural hatred of mankind, his desire to get even with them, his avarice; and, consequently, his chances of being dishonest will be increased. The Jupiterian will rarely be found with such an indication; when he is, some one of the three types just mentioned will be strong also, and the traits indicated by the absent Heart line will come from their side of the house.
 
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