the body, particularly the thoracic muscles, of the mosquito. The exact mode of migration of the parasite from the mosquito to the man is yet undetermined; whether by the bite, that is, the piercing of the skin with the oral proboscis, or whether it occurs by the drinking of water in which the dead bodies of the infested mosquitoes have disintegrated, is still undetermined. The filariæ have been observed to migrate from the thorax of the mosquito into its labium (the fleshy sheath of the proboscis), and even to escape from the tip of the labium. This points strongly to the possibility of infection at the time of piercing, but the parasites are large, and few could enter the blood at one time. The disease has obtained an amazing prevalency among the natives, almost certainly one-third or more Manson estimates it at one-half being afflicted. It is incurable, at least in all cases of a certain length of standing, and even from the first if the patient remains in the tropics. It causes the patient little pain, being attended, however, at certain recurring intervals by fever, but in its advanced stages so deforms the body as to make the sufferer incapable of walking or of almost any other motion. White men are occasionally attacked; one white patient was seen near Pago-Pago during our stay. If the disease once seated is incurable, remedial measures must be in the nature of a campaign against the intermediary mosquito, the most abundant species of which is, interestingly enough, the same species, Stegomyia fasciata, so abundant in Cuba, and by the researches of American surgeons and physicians now practically convicted of breeding and disseminating the (still unknown) parasite of yellow fever. So far as the Samoan people are concerned the most valuable possible result of American rule would be the stamping out of the mosquito in Tutuila, and steps in this direction have already been taken. Atlantic, 94: 632. Connecting New Ideas with Old. 105. When the cause of the difficulty is the strangeness or disconnectedness of the subject, the aim of the expositor is to discover some connection, now hidden from us, between the new idea and ideas that are old and familiar. He tries to place the new thought in a system of ideas which we already understand. This method of explanation is well illustrated in the selection below. The subject which the author wishes to explain, the fourth dimension, is to most of us wholly strange and mysterious. It has no place, apparently, in the order of ideas with which we are familiar. our notions about it are extremely vague and confused. On the other hand, we are all perfectly familiar with the ordinary geometrical conceptions of parallel lines, spheres, and plane surfaces; and if the fourth dimension can somehow be connected naturally with these familiar and systematized conceptions, it is very likely to be understood. The connection is made by the writer as follows: Hence Suppose a world consisting of a boundless flat plane to be inhabited by reasoning beings who can move about at pleasure on the plane, but are not able to turn their heads up or down, or even to see or think of such terms as above them and below them, and things around them can be pushed or pulled about in any direction, but cannot be lifted from the plane. People and things can pass around each other, but cannot step over anything. These dwellers in "flatland" could construct a plane geometry which would be exactly like ours in being based on the axioms of Euclid. Two parallel straight lines would never meet, though continued indefinitely. But suppose that the surface on which these beings live, instead of being an infinitely extended plane, is really the surface of an immense globe, like the earth on which we live. It needs no knowledge of geometry, but only an examination of any globular object—an apple, for example - to show that if we draw a line as straight as possible on a sphere, and parallel to it draw a small piece of a second line, and continue this in as straight a line as we can, the two lines will meet when we proceed in either direction onequarter of the way around the sphere. For our "flat-land" people these lines would both be perfectly straight, because the only curvature would be in the direction downwards which they could never either perceive or discover. To explain hypergeometry proper we must first set forth what a fourth dimension of space means, and show how natural the way by which it may be approached. We continue our analogy from "flat-land." In this supposed land let us make a cross - two straight lines intersecting at right angles. The inhabitants of this land understand the cross perfectly and conceive of it just as we do. them to draw a third line, intersecting in and perpendicular to both the other lines. once pronounce this absurd and impossible. It is equally absurd and impossible to us if we require the third line to be drawn on the paper. But we should reply, “If you allow us to leave the paper or flat surface, then we can solve the problem by simply drawing the third line through the paper perpendicular to its surface." But let us ask the same point, They would at Now, to pursue the analogy, suppose that, after we have drawn three mutually perpendicular lines, some being from another sphere proposes to us the drawing of a fourth line. through the same point, perpendicular to all three of the lines already there. We should answer him in the same way that the inhabitants of "flat-land" answered us: “The problem is impossible. You cannot draw any such line in space as we understand it." If our visitor conceived of the fourth dimension, he would reply to us as we replied to the "flat-land" people: "The problem is absurd and impossible you confine your line to space as you understand it. But for me there is a fourth dimension in space. Draw your if line through that dimension and the problem will be solved. This is perfectly simple to me; it is impossible to you solely because your conceptions do not admit of more than three dimensions." Supposing the inhabitants of "flat-land " to be intellectual beings as we are, it would be interesting to them to be told what dwellers of space in three dimensions could do. Let us pursue the analogy by showing what dwellers in four dimensions might do. Place a dweller of "flat-land” inside a circle drawn on his plane, and ask him to step outside of it without breaking through it. He would go all around, and finding every inch of it closed, he would say it was impossible from the very nature of the conditions. "But," we would reply, "that is because of your limited conceptions. We can step over it." Step over it!" he would exclaim. "I do not know what that means. I can pass around anything if there is a way open, but I cannot imagine what you mean by stepping over it." But we should simply step over the line and reappear on the other side. So, if we confined a being able to move in a fourth dimension in the walls of a dungeon of which the sides, the floor, and the ceiling were all impenetrable, he would step outside of it without touching any part of the building, just as easily as we could step over a circle drawn on the plane without touching it. To do this he would only have to make a little excursion in the fourth dimension. Harper's Magazine, 104: 249. 106. Assignments on Connecting New Ideas with Old. A. Explain to a pupil in the first year of the high school the meaning of one of the following terms. Try to connect the strange idea with ideas that are familiar to him. Make an effort to put yourself in his place, for in this way you can more readily think of the things he knows about and will be interested in. Beware of using terms that he will not understand. (1) Wireless telegraphy. (2) A trust. (3) Hypnotism. (4) The New England town-meeting. (5) Reciprocity. (6) The canals of Mars. (7) The solar spectrum. (8) The referendum. (9) The shorter catechism. (10) The facial angle. (11) Graft. (12) Monopoly. (13) Monoplane. (14) Political Insurgency. (15) Embezzlement. (16) Kleptomania. (17) Volt. (18) Ohm. (19) H.P. (20) F.O.B. B. A boy ten years old wishes to know why it is that a spoon when it is put in a glass of water looks as if it were bent or broken. Explain the phenomenon to him in simple terms. C. Explain to a younger person what you think Emerson meant when he said, "Good manners are made up of petty sacrifices." Use familiar examples. D. Suppose that a laboring man who has had but little education has brought to you the following lines of poetry for explanation. He has found them in Shakespeare's Julius Caesar, which he is now, with interest but with difficulty, reading for the first time. What will you say to him? Remember that many things with which you are well acquainted will be to him very new and strange. Between the acting of a dreadful thing Act II, Sc. 1. |