plate having in one edge the female character or matrix proper, and in the upper end a series of teeth, used as hereinafter explained for distributing the matrices after use to their proper places in the magazine of the machine. There are in the machine a number of matrices for each letter and also matrices representing special characters, and spaces or quadrats of different thicknesses for use in table-work. There is a series of finger keys representing the various characters and spaces, and the machine is so organized that on manipulating the keys it selects the matrices in the order in which their characters are to appear in print, and assembles them in a line, with wedge-shaped spaces or justifiers between the words. The series of matrices thus assembled in line forms a line matrix, or, in other words, a line of female dies adapted to mold or form a line of raised type on a slug cast against the matrices. After the matrix line is composed, it is automatically transferred to the face of a slotted mold into which molten type-metal is delivered to form a slug or linotype against the matrices. This done, the matrices are returned to the magazine and distributed, to be again composed in new relations for succeeding lines.
[Illustration: Fig. 2.]
Fig. 2 illustrates the general organization of the machine.
A represents an inclined channelled magazine in which the matrices are stored. Each channel has at the lower end an escapement B to release the matrices one at a time. Each of these escapements is connected by a rod C and intermediate devices to one of the finger-keys in the keyboard D. These keys represent the various characters as in a typewriter. The keys are depressed in the order in which the characters and spaces are to appear, and the matricies, released successively from the lower end of the magazine, descend between the guides E to the surface of an inclined travelling belt F, by which

by muscles when it has to serve as a lever. Even when we take a pen in our hand and write, these engines which balance and fix the wrist have to be in action all the time. The steadiness of our writing depends on how delicately they are balanced. Like the muscles of the foot, the fixers of the wrist may become overworked and exhausted, as occasionally happens in men and women who do not hold their pens correctly and write for long spells day after day. The break-down which happens in them is called "writer's cramp," but it is a disaster of the same kind as that which overtakes the foot when its arch collapses, and its utility as a lever is lost.
FOOTNOTES:
[Footnote 1: From The Engines of the Human Body, Chapters VI and VII. J.B. Lippincott Company, Philadelphia, 1920; Williams and Norgate, London, 1920.]
THE EXPOSITION OF A MACHINE
THE MERGENTHALER LINOTYPE[2]
_Philip T. Dodge_
The Mergenthaler Linotype machine appeared in crude form about 1886. This machine differs widely from all others in that it is adapted to produce the type-faces for each line properly justified on the edge of a solid slug or linotype.
These slugs, automatically produced and assembled by the machine, are used in the same manner as other type-forms, whether for direct printing or for electrotyping, and are remelted after use.
GENERAL ORGANIZATION
The general organization of the machine will first be described. After this the details will be more fully explained and attention plainly directed to the various parts which require special consideration.
[Illustration: Fig. 1.]
The machine contains, as the vital element, about sixteen hundred matrices, such as are shown in Fig. 1, each consisting of a small brass

diminished. We can see, then, why the humerus is short and the forearm long in anthropoid apes; shortening the humerus makes it more powerful as a lever for lifting the body. That is why anthropoids are strong and agile tree-climbers. But then watch them use those long hands and forearms for the varied and precise movements we have to perform in our daily lives, and you will see how clumsy they are.
[Illustration: Fig. 10.--Showing the action of the brachialis anticus in the arm of an anthropoid ape.]
In the human machine the levers of the arm have been fashioned, not for climbing, but for work of another kind--the kind which brings us a livelihood. We must have perfect control over our hands; the longer the lever of the forearm is made, the more difficult does control of the hand become. Hence, in the human machine the forearm is made relatively short and the upper arm long.
We have just seen that the brachial muscle could at one time move the forearm and hand, but that when they are fixed it could then use the humerus as a lever and thereby lift the weight of the body. What should we think of a metal engine which could reverse its action so that it could act through its piston-rod at one time and through its cylinder at another? Yet that is what a great number of the muscular engines of the human machine do every day.
There is another little point, but an important one, which I must mention before this chapter is finished. I have spoken of the forearm and hand as if they formed a single solid lever. Of course that is not so; there are joints at the wrist where the hand can be moved on the forearm. But when a weight is placed in the hand, these joints became fixed by the action of muscles. The fixing muscles are placed in the forearm, both in front and behind, and are set in action the moment the hand is loaded. The wrist joint is fixed just in the same way as the joints of the foot are made rigid

forearm and hand are ill adapted for lifting heavy burdens; strength is sacrificed if they are too long. Hence, we find that the laboring peoples of the world--Europeans and Mongolians--have usually short forearms and hands, while the peoples who live on such bounties as Nature may provide for them have relatively long forearms and hands.
[Illustration: Fig. 9B.--The forearm and hand as a lever of the third order.]
Now, man differs from anthropoid apes, which are distant cousins of his, in having a forearm which is considerably shorter than the upper arm; whereas in anthropoid apes the forearm is much the longer. That fact surprises us at first, especially when we remember that anthropoids spend most of their lives amongst trees and use their arms much more than their legs in swinging the weight of their heavy bodies from branch to branch and from tree to tree. A long forearm and hand give them a long and quick reach, so that they can seize distant branches and swing themselves along safely and at a good pace. Our first thought is to suppose that a long forearm, being a weak lever, will be ill adapted for climbing. But when you look at Fig. 10, the explanation becomes plain. When a branch is seized by the hand, and the whole weight of the body is supported from it, the entire machinery of the arm changes its action. The forearm is no longer the lever which the brachial muscle moves (Fig. 10), but now becomes the base from which it acts. The part which was its piston cord now serves as its base of fixation, and what was its base of fixation to the humerus becomes its piston cord. The humerus has become a lever of the third order; its fulcrum is at the elbow; the weight of the body is attached to it at the shoulder and represents the load which has to be lifted. We also notice that the brachial muscle is attached a long way up the humerus, thus increasing its power very greatly, although the rate at which it helps in lifting the body is

fulcrum (Fig. 9 B). At the opposite end of the lever, in the, upturned palm of the hand, we shall place a weight of 1 lb. to represent the load to be moved. The power which we are to yoke to the lever is a strong muscular engine we have not mentioned before, called the brachialis anticus, or front brachial muscle. It lies in the upper arm, where it is fixed to the bone of that part--the humerus. It is attached to one of the bones of the forearm--the ulna--just beyond the elbow.
In the second order of lever, we have seen that the muscle worked on one end, while the weight rested on the lever somewhere between the muscular attachment and the fulcrum. In levers of the third order, the load is placed at the end of the lever, and the muscle is attached somewhere between the load and the fulcrum (Fig. 9 A). In the example we are considering, the brachial muscle is attached about half an inch beyond the fulcrum at the elbow, while the total length of the lever, measured from the elbow to the palm, is 12 inches. Now, it is very evident that the muscle or power being attached so close to the elbow, works under a great disadvantage as regards strength. It could lift a 24-lb. weight placed on the forearm directly over its attachment as easily as a single pound weight placed on the palm. But, then, there is this advantage: the 1-lb. weight placed in the hand moves with twenty-four times the speed of the 24-lb. weight situated near the elbow. What is lost in strength is gained in speed. Whenever Nature wishes to move a light load quickly, she employs levers of the third order.
[Illustration: Fig. 9A.--A chisel used as a lever of the third order. W, weight; P, power; F, fulcrum.]
We have often to move our forearm very quickly, sometimes to save our lives. The difference of one-hundredth of a second may mean life or death to us on the face of a cliff when we clutch at a branch or jutting rock to save a fall. The quickness of a blow we give or fend depends on the length of our reach. A long

installation of seventeen small engines, all of them springing into action when we stand up, thus helping to maintain the foot as a rigid yet flexible lever.
We have already seen why our muscles are so easily exhausted when we stand stock-still; they then get no rest at all. Now, it sometimes happens in people who have to stand for long periods at a stretch that these muscular engines which maintain the arch are overtaxed; the arch of the foot gives way. The foot becomes flat and flexible, and can no longer serve as a lever. Many men and women thus become permanently crippled; they cannot step off their toes, but must shuffle along on the inner sides of their feet. But if the case of the overworked muscles which maintain the arch is hard in grown-up people, it is even harder in boys and girls who have to stand quite still for a long time, or who have to carry such burdens as are beyond their strength. When we are young, the bony levers and muscular engines of our feet have not only their daily work to do, but they have continually to effect those wonderful alterations which we call growth. Hence, the muscular engines of young people need special care; they must be given plenty of work to do, but that kind of active action which gives them alternate strokes of work and rest. Even the engine of a motor cycle has three strokes of play for one of work. Our engines, too, must have a liberal supply of the right kind of fuel. But even with all those precautions, we have to confess that the muscular engines of the foot do sometimes break down, and the leverage of the foot becomes threatened. Nor have we succeeded in finding out why they are so liable to break down in some boys and girls and not in others. Some day we shall discover this too.
We are now to look at another part of the human machine so that we may study a lever of the third order. The lever formed by the forearm and hand will suit our purpose very well. It is pivoted or jointed at the elbow; the elbow is its

limits of the most effective working radius of the lever. It is a law for all the levers of the body; they are set and moved in such a way as to avoid the occurrence of dead centres. Think what our condition would have been were this not so; why, we should require revolving fly-wheels set in all our joints!
[Illustration: Fig. 8.--The arch of the foot from the inner side, showing some of the muscles which maintain it.]
Another property is essential in a lever: it must be rigid; otherwise it will bend, and power will be lost. Now, if the foot were a rigid lever, there would be missing two of its most useful qualities. It could no longer act as a spring or buffer to the body, nor could it adapt its sole to the various kinds of surfaces on which we have to tread or stand. Nature, with her usual ingenuity, has succeeded in combining those opposing qualities--rigidity, suppleness, and elasticity or springiness--by resorting to her favorite device, the use of muscular engines. The arch is necessarily constructed of a number of bones which can move on each other to a certain extent, so that the foot may adapt itself to all kinds of roads and paths. It is true that the bones of the arch are loosely bound together by passive ties or ligaments, but as these cannot be lengthened or shortened at will, Nature had to fall back on the use of muscular engines for the maintenance of the foot as an arched lever. Some of these are shown in Fig. 8. The foot, then, is a lever of a very remarkable kind; all the time we stand or walk, its rigidity, its power to serve as a lever, has to be maintained by an elaborate battery of muscular engines all kept constantly at work. No wonder our feet and legs become tired when we have to stand a great deal. Some of these engines, the larger ones, are kept in the leg, but their tendons or piston cords descend below the ankle-joint to be fixed to various parts of the arch, and thus help to keep it up (Fig. 8). Within the sole of the foot has been placed an

piston is in the position shown in Fig. 7, B. Then the leverage decreases until the second dead centre is reached (Fig. 7, C); from that point the leverage is increased until the second maximum is reached (Fig. 7, D), whereafter it decreases until the arrival at the first position completes the cycle. Thus, in each revolution there are two points where all leverage or power is lost, points which are surmounted because of the momentum given by the flywheel. Clearly we should get most out of an engine if it could be kept working near the points of maximum leverage--with the lever as nearly as possible at right angles to the crank-pin.
[Illustration: Fig. 7.--Showing the crank-pin of an engine at: A, First dead centre. B, First maximum leverage. C, Second dead centre. D, Second maximum leverage.]
Now, we have seen that the tendon of Achilles is the piston cord, and the heel the crank-pin, of the muscular engine represented by the gastrocnemius and soleus. In the standing posture the heel slopes downwards and backwards, and is thus in a position, as regards its piston cord, considerably beyond the point of maximum leverage. As the heel is lifted by the muscles, it gradually becomes horizontal and at right angles to its tendon or piston cord. As the heel rises, then, it becomes a more effective lever; the muscles gain in power. The more the foot is arched, the more obliquely is the heel set and the greater is the strength needed to start it moving. Hence, races like the European and Mongolian, which have short as well as steeply set heels, need large calf muscles. It is at the end of the upward stroke that the heel becomes most effective as a lever, and it is just then that we most need power to propel our bodies in a forward direction. It will be noted that the heel, unlike the crank-pin of an engine, never reaches, never even approaches, that point of powerlessness known to engineers as a dead centre. Work is always performed within the

[Illustration: Fig. 6.--The bones forming the arch of the foot, seen from the inner side.]
If we had the power to make our heels longer or shorter at will, we should be able, as is the case in a motor cycle, to alter our "speed-gear" according to the needs of the road. With a steep hill in front of us, we should adopt a long, slow, powerful heel; while going down an incline a short one would best suit our needs. With its four-change speed-gear a motor cycle seems better adapted for easy and economical travelling than the human machine. If, however, the human machine has no change of gear, it has one very marvellous mechanism--which we may call a compensatory mechanism, for want of a short, easy name. The more we walk, the more we go hill-climbing, the more powerful do the muscular engines of the heel become. It is quite different with the engine of a motor cycle; the more it is used, the more does it become worn out. It is because a muscular engine is living that it can respond to work by growing stronger and quicker.
I have no wish to extol the human machine unduly, nor to run down the motor cycle because of certain defects. There is one defect, however, which is inherent in all motor machines which man has invented, but from which the human machine is almost completely free. We can illustrate the defect best by comparing the movements of the heel with those of the crank-pin of an engine. One serves as the lever by which the gastrocnemius helps to propel the body; the other serves the same purpose in the propulsion of a motor cycle. On referring to Fig. 7, A, the reader will see that the piston-rod and the crank-pin are in a straight line; in such a position the engine is powerless to move the crank-pin until the flywheel is started, thus setting the crank-pin in motion. Once started, the leverage increases, until the crank-pin stands at right angles to the piston-rod--a point of maximum power which is reached when the

sole in line with the ball of the great toe, serves as a fulcrum or rest. The weight of the body falls on the foot between the fulcrum in front and the power behind, as in a lever of the second order. We have explained why the power of the muscles of the calf is increased the more the weight of the body is shifted towards the toes, but it is also evident that the speed and the extent to which the body is lifted are diminished. If, however, the weight be shifted more towards the heel, the muscles of the calf, although losing in power, can lift their load more quickly and to a greater extent.
We must look closely at the foot lever if we are to understand it. It is arched or bent; the front pillar of the arch stretches from the summit or keystone, where the weight of the body is poised, to the pad of the foot or fulcrum (Fig. 6); the posterior pillar, projecting as the heel, extends from the summit to the point at which the muscular power is applied. A foot with a short anterior pillar and a long posterior pillar or heel is one designed for power, not speed. It is one which will serve a hill-climber well or a heavy, corpulent man. The opposite kind, one with a short heel and a long pillar in front, is well adapted for running and sprinting--for speed. Now, we do find among the various races of mankind that some have been given long heels, such as the dark-skinned natives of Africa and of Australia, while other races have been given relatively short, stumpy heels, of which sort the natives of Europe and of China may be cited as examples. With long heels less powerful muscular engines are required, and hence in dark races the calf of the leg is but ill developed, because the muscles which move the heel are small. We must admit, however, that the gait of dark-skinned races is usually easy and graceful. We Europeans, on the other hand, having short heels, need more powerful muscles to move them, and hence our calves are usually well developed, but our gait is apt to be jerky.