when almost falling to pieces with age. Ours we returned afterward to all the various donors. Knowing their value we had not the heart to retain them when we left Samoa.

At two o'clock the coffin was brought out by a dozen powerful Samoans, who led the way with it up the mountain. Directly behind were thirty or forty more men, who at intervals changed places with the bearers. It was a point of honor with them all to keep their heavy burden shoulder-high, though how they contrived to do so on that precipitous path was a seeming impossibility. A party of a score or more white people followed, interspersed with chiefs of high rank. Behind these, again, were perhaps two hundred Samoans, all in the white singlets and black lavalavas which had been given them for that day of mourning.

The sun shone mercilessly; the heat was stifling; but of course our own feeling was one of thankfulness that rain had not intervened. A heavy rain in Samoa is a veritable cloudburst. We should never have been able to make the path had it rained, and the whole interment would have been robbed of its dignity and beauty. But the heat made it a terrible climb for some of our guests. There was one elderly white man who I thought would never reach the summit alive. We knew him but slightly; were surprised, indeed, to see him; I doubt if Stevenson had ever spoken to him more than half a dozen times.

"I am going on if it kills me," he said, deaf to all our entreaties to turn back. "I venerated Stevenson; he shall not be

laid in his grave without my last tribute of respect.

With mottled face, shirt half open, gasping for breath and occasionally lying down while we fanned him, he persevered with an almost irritating obstinacy. But I really believe it did kill him, for the poor fellow was ill for a month afterward and then died. There were others who looked almost as spent, but who were animated by a similar resolution. The photographs of Mount Vaea, like all photographs of mountains, diminish its height; it would be easy for one who has seen it only in pictures to get a very mistaken impression. From Vailima to the summit is a most formidable ascent for sedentary people unaccustomed to exercise.

We gathered about the grave, and no cathedral could have seemed nobler nor more hallowed than the grandeur of nature that encompassed us. What fabric of men's hands could vie with so sublime a solitude? The sea in front, the primeval forest behind, crags, precipices, and distant cataracts gleaming in an untrodden wilderness. The words of the Church of England service, movingly delivered, broke the silence in which we stood. The coffin was lowered; flowers were strewn on it, and then the hurrying spades began to throw back the earth.

"Under the wide and starry sky,
Dig the grave and let me lie.
Glad did I live and gladly die,

And I laid me down with a will.

This be the verse you grave for me: Here he lies where he longed to be; Home is the sailor, home from sea,

And the hunter home from the hill.”

N human society, communication is either by transportation or transmission. We post a letter, which is carried to its destination in due course of time; or we call our friend on the telephone, speaking the information, which is instantly transmitted. The human organism, the individual, likewise possesses these two means of connecting the various parts of his body.

There are the hormones, chemical messengers, definite substances, drugs if you like, produced in one part of the body, which are carried in the blood stream to some other organ upon which they exert their specific effects. Chemical co-ordination and regulation result.

For example, our muscles, during rapid exercise, produce large quantities of carbon dioxide, which, passing into the blood, is carried to the respiratory centre in the brain and stimulates it to greater activity. Breathing becomes more rapid, and the excess of carbon dioxide in the blood thereby eliminated. The muscles have posted a letter, which is received and acted on by the respiratory centre. So each ductless gland in the body sends its message to some other organ through this common postal system of the individual. But more important still, the body has its telephone-wires, the nervous system, by which messages are transmitted far more rapidly and efficiently. Chance contact with a needle-point causes our finger to be drawn back automatically and instantly. Nervous co-ordination and regulation result. Little do we realize the complicated series of events which follow one another in the performance of even so rapid and simple an act as this.

Again, the image of some object on our retina produces an effect in the optic nerve

which is carried to the brain. There appear sensations, the consciousness of that retinal image, memories, "airy thoughts like purple birds that shine and soar."

What is the nature of this influence in the nerve, the go-between of the objective and subjective world? While some question, and others affirm, the reality of thought-transferrence between the living, and many insist on spiritualistic communication with the dead, let us examine that type of nervous activity, borne along pathways that are known and subject to every query that an active mind may devise. We call it the nerve-principle, nerve-force, nerve-energy, nerve-wave, perhaps best the nerve-impulse. Despite the apparent mystery of the process and the minute size of nerve-fibres, it is safe to say that more is known about the nerveimpulse than any other subject in physiological neurology. But this information has not come at a bound.

The ancients thought our nerves were tubes through which flowed a gas, the "animal spirits," or a liquid, the "nervejuice." It is now quite certain that nothing flows, but something is transmitted. Galvani, in 1786, identified the impulse with electricity, since nerves could be stimulated by electric currents. DuBois Reymond, in 1843, discovered an electric current, the "action current," which accompanied the passage of a nerve-impulse. This was thought to confirm the idea that a nerve-impulse was identical with electricity. Even those physiologists of the time who were opposed to the identity of electricity and nerve-impulses, nevertheless believed that the nerve-impulse moved with the velocity of light, and stated that we should never be able to measure the velocity of the nerve-impulse in the short distances available in the body of an animal. In 1852 Von Helmholtz actually measured the rate of the

impulse in a frog, and found that its velocity was quite finite and relatively slow, eighty-eight feet per second, far slower in fact than the velocity of sound. Thus, the investigation of nerve-impulses was placed on a scientific basis, for when we can measure a thing, we can talk about it intelligently.

The rate in man was later found to be four hundred and twenty-six feet per second, nearly five times as fast as the frog. Other animals possess nerves whose impulses move at different rates. In inver

tebrates the rate is unusually slow, and in some forms the nervous structure is such as to allow not only a determination of the speed of the nerve-impulse but a study of the effects of temperature, anæsthetics, or fatigue on the rate of the impulse with an accuracy and simplicity quite unparalleled in biological research.

By an ingenious bit of scientific machination the late Doctor Alfred G. Mayor, director of the Tortugas Laboratory of the Carnegie Institution of Washington, obtained nerve tissue in a jelly-fish which

for all practical purposes is hundreds of miles in length. Moreover, the impulse could be watched as it progressed because of the contraction of muscles associated with the nerve tissue. First observed in 1905, Doctor Mayor's experiment and others following called attention to such extraordinarily favorable material for study of nerve-impulses that this jelly-fish, Cassiopea by name, deserves to go down in physiological his

spontaneous movement of the jelly-fish then ceases. We now have a flat disk of living nerve-muscle tissue which remains perfectly quiescent unless stimulated in some way.

Suppose we cut the disk into the shape of a ring, like a doughnut (Fig. 1), and then stimulate some portion of the ring. Two nerve-impulses, visible as two waves of muscle contraction, now start off passing around the ring in opposite directions, as

S

Block

S

tory as classic, along with the frog and the turtle.

The animal, shown in Fig. 1, lives in the calm waters of a moat surrounding old Fort Jefferson near the Tortugas Laboratory, off the Florida coast. Its nervous system is most primitive, a mere network of nerve tissue spread over the flattened concave disk of the animal. Underneath the nerves is a layer of muscle tissue, circular and radial muscles, whose contraction pushes the jelly-fish through the water by a series of pulses. The nerves connect with sense-organs along the edge of the disk, in which stimuli arise that pass over the nerve network and in turn stimulate the muscles. Thus the creature progresses by a series of contractions like the beating of a heart.

That the sense-organs are really centres of origin for stimuli can be shown by cutting them away from the disk. All

shown in Fig. 2. They meet at the far edge of the ring and block each other. This is an interesting fact in itself, that two nerveimpulses in collision block each other.

But suppose we could block one of the two impulses moving in opposite directions about a ring before they met and blocked each other. The unblocked impulse would now meet no obstacle and would pass around the ring continuously in one direction. As it passed, the muscles would contract, and we could thus watch its progress.

Such an experiment can readily be performed by pressing on the tissue with a glass rod while stimulating at S, Fig. 2. Pressure on a nerve will block nerve-impulses in the nerve. This is what happens when our foot goes to sleep. Pressure on the foot-nerves blocks impulses, and so our foot feels numb and muscles in the foot cannot be moved.

trapped a nerve-impulse! There is nothing to stop it, and theoretically it might go forever. It is quite possible to record the passage of such a nerve-wave on a piece of smoked paper wound on a revolvingdrum, as shown in Fig. 3.

I have actually succeeded in keeping such rings with nerve-impulses moving for eleven days without a stop and with no marked change in the rate of the nerveimpulse, which travelled in all four hundred and fifty-seven miles. At the end

sue would decay in eleven days. Not so; on the contrary, the missing parts begin to regenerate, and it is the partial reformation of the sense-organs which generate other impulses that finally block the entrapped wave. Otherwise the impulse might travel considerably farther.

A very important conclusion can be drawn from the above experiment; namely, that an impulse belongs in the group of self-propagative disturbances which travel without decrement. It may be