condensation meets with a rarefaction, and | three instruments the vibrator, the in this case both actions neutralize each screen, and the detector-the experiother-the sound is weakened. So that, ments could be carried on, and they if we slowly approach our reflecting board proved at once the close connection exto the fork, there will be places where the isting between the phenomena of elecboard reinforces the sound (condensations tricity and light. meeting with condensations), then weak- As soon as sparking began in the ens it, and then makes it louder again, vibrator, and the detector was approached although the board is moved all the time to it, sparks began to jerk between the in one direction, towards the tuning-fork. knobs of the latter; but they disappeared Of course, things are not so easy with as soon as the screen was interposed beelectricity. There is no great difficulty tween the two- the "waves" being interin producing alternate electrifications of rupted in this case. On the contrary, the surrounding ether which would corre- when the screen was placed immediately spond to the alternate condensations of behind the detector, strong sparking folthe air, but they must follow each other lowed; if it was removed about eighteen with a tremendous rapidity. In fact, if feet, the sparking ceased; the direct and the tuning-fork makes, say, one thousand the reflected waves extinguishing each vibrations in the second-the speed of other; but when the screen was moved sound in dry air being but eleven hundred away for another eighteen feet, sparking feet in the same time-a condensation reappeared the two waves reinforcing will only have travelled a little over one each other, and so on. In short, the phefoot before a new condensation follows it. nomena were exactly like those which The "waves" of sound will be I'I foot would be noticed if a tuning-fork, a relong. But if our electrical discharges flecting board, and a resonator were used. also succeeded each other with a fre- It was thus proved that each electrical quency of no more than one thousand dis-discharge produces some disturbance in charges in a second, the electric wave (supposing that it spreads at the rate of one hundred and eighty thousand miles in a second, like light) would have travelled one hundred and eighty miles before a new wave would be originated by the next discharge. And waves of that length are not easy to deal with. So that, in order to obtain waves of a reasonable length following each other at a distance of, say, thirty-five or forty feet-Hertz had to produce discharges alternating thirty million times in a second. So he did. He obtained such rapid discharges for very short intervals of time, and thus he could measure the distances at which the electrical "waves" followed each other. A reflecting board, and some means for detecting the "loops and nodes," ie., the places where the waves reinforce or extinguish each other, were the next requisites. A reflecting board was readily made out of a sheet of zinc, ten to twelve feet square. As to the "detector," Hertz chose, out of the various means at his disposal, a brass wire, provided with two knobs and bent into a ring, which could give sparks when it received electrical waves of a certain length. With these Thirty million times thirty-five feet would make one hundred and eighty thousand miles. To attain a very rapid succession of alternate electrifications, Hertz used two brass plates, twelve inches square, to each of which was attached a thick wire, about two inches long, terminated by a brass knob. The distance between the two knobs was very small-less the surrounding space; that the disturb. ance is transmitted, through the "nonconductive" air, exactly as luminous or sound vibrations are transmitted; and that electricity is propagated, like heat and light, at some finite and measurable speed. Of course it would not be possible to give here the tedious processes by which the measurements were made, nor to tell the difficulties, the doubts, and the seemingly contradictory facts which were met with in the way; although dating from yesterday, "Hertz's experiments" have already a whole history. Suffice it to say, that the velocity of electricity, both in the air and the conductive wires, proved to be very near to that of light, namely, about one hundred and eighty thousand miles in a second. than one-tenth of an inch. When the plates were elec trified by an induction coil, a series of sparks jerked from one knob to the other, the charge rapidly passing forwards and backwards, and giving very rapid alternative discharges. This was the "vibrator." As to the "detector," or "resonator," it consisted of a thick wire, the two ends of which were provided with brass knobs, and the length of which was taken so as to suit the oscillations in the vibrators. The wire being bent into a circle, its two knobs were brought very near to each other, so as to show sparks at the reception of the feeblest electric waves (Sitzungsberichte der Berliner Acad. der Wissenschaften, February 9, 1888). It hardly needs adding that during the experiments the reflecting board, or the apparatus used instead, remained stationary, and that the resonator was moved instead of it. For more details see an excellent résumé in the last chapter of Th. Preston's "Theory of Light,' London, 1890. The general reader may consult the very good papers in Nature, March 5 and 14, 1890. to verify the experiments; and so they were verified by several physicists - in this country by Professor Fitzgerald and Fr. Trutton at Dublin,* and by Professor Lodge and Mr. Dragoumis at Liverpool.† In fact, Professor Lodge had nearly discovered the same phenomena simultaneously with Hertz, as he was making in 1887 and 1888 his experiments on the rapid discharges obtained from Leyden_jars.‡ Blondlot, in France, slightly modifying the primitive experiments, finally settled the velocity of electricity in the air at from two hundred and ninety-one thousand to three hundred and four thousand kilomè tres in the second, thus very nearly approaching to the velocities of light.§ Then, Hertz himself having been brought by his earlier measurements to admit that the speed of the electrical disturbances is much smaller in wires than in the surrounding air, more careful measurements were required, and they were made in Geneva and in Germany, and proved that the velocity, as foreseen by theory, is equal in both cases.|| This may be considered as the first part | and, in fact, nearly all that is now written of the experiments. The second part is upon electricity is in some way connected even more interesting, as it disclosed fur- with them. First of all, it was necessary ther analogies between electro-magnetism and light. Light is transmitted by some bodies, and is reflected by other bodies. Electro-magnetic waves behave in the same way; a plate of zinc acts upon them as a mirror and sends them back, but they pass through a wooden door just as light passes through a window plate. Hertz could send them into the next room through a shut door. If we put a red-hot iron ball in the focus of a parabolic mirror, we may make it light a match adjusted in the focus of another parabolic mirror which is placed at the other end of a room. Electricity behaves in the same way; we can send beams of electrical oscillations by means of a parabolic mirror, and intercept them at a distance by another mirror and send them into its focus. If we in. terrupt the initial discharges in a certain way- -as they are interrupted in the Morse alphabet we shall transmit electrical signals and have a telegraph without connecting wires. Light is refracted by transparent bodies if they have the shape of a prism or a lens; and by means of a big prism of pitch Hertz refracted the electro-magnetic "rays; " he could bend them, and send them under a right angle into another room. Reflected light can be polarized, and electro-magnetic "rays" are polarized, too. In short, Maxwell's hypothesis as to the identity of light and electricity is fully confirmed. Both are disturbances (vibrations, or whatever they might be) in the usual state of ether which are transmitted like all other kinds of energy -like the energy of the billiard ball, the stone, and the tuning-fork, of which we spoke at the beginning of this chapter, that is, from one particle to the next. So we finally part with the mysterious "electric fluid "just as we parted, thirty years ago, with the "caloric fluid," and we simply have before us a separate mode of energy. When the waves of ether have lengths of from '000012 to 000016 parts of an inch, we have chemical energy; when they follow each other at distances of from 000016 to 00003 parts of the incb, our eye sees them as light; when they grew to 00012 parts of the inch, we 'see them no more, but we feel them as radiant heat; and when they attain lengths which are measured by yards and miles, they give the electrical phenomena. A wide series of researches was evidently called into life by these researches, Another important matter was to study the magnetic part of the same electric disturbances. In Maxwell's theory the magnetic disturbances ought to be nothing but transversal rotations of the particles of ether in a plane perpendicular to the line of transmission of light and electricity "molecular vortices," as he used to say. And Hertz succeeded in proving by a new series of experiments-or, at least, in rendering it most probable that the magnetic force obeys in its transmission the same laws as electricity, but that the direction of its vibrations is perpendicular to the line of transmission of the electric waves; and he made at the same time an attempt at measuring the mechanical effects of the electric disturbances.** Nature, vol. xxxix., p. 391, vol. xli., p. 295. ↑ Ib. vol. xxxix., p. 548. Society (vol. 1., No. 302, August 28, 1891): "This same + Prof. Lodge writes, in the Proceedings of the Royal discovery (Hertz's) would have been made by the audi8, 1889, if it had not been made before; for, during a ence at the Royal Institution on the evening of March lecture on Leyden jars, every time one was discharged through a considerable length of wire, the heavily gilt wall paper sparkled brightly by reason of the incident radiation. § Comptes Rendus, 1891, t. 112, P, 1058; t. 113, p. 628. Sarasin et L. de la Rive in Comptes Rendus, 1891, t. 112, Nos. 12 et 13; Rubens and Ritter in Wiede mann's Annalen der Physik, 1890, vol. xl. T See $ 822 of Maxwell's Treatise on Electricity and Magnetism, second edition, 1881. "Ueber die mechanischen Wirkungen electrischer At the same time a further confirmation | mathematical and highly suggestive as of the light theory of electricity was given regards the very structure of matter, and by Arons and Rubens, who proved that some others opening new fields for experthe relation which, according to Maxwell, imental work, like J. J. Thomson's reought to exist between the isolating power searches into the speed of propagation of of various substances and their powers of the luminous discharge of electricity refracting the rays of light, exists in real-through a rarefied gas,f and Hertz's new ity. The resistance offered to the passage experiments upon the transmission of the of light and that offered to the passage of same discharges through various screens, electricity are connected by a simple rela- transparent or not for light‡- might be tion. On the other side, Sir William mentioned in connection with the above. Thomson read before the Royal Society a But we must say, at least, a few words most interesting paper on the screens, about the quite new lines of research inand their efficiency against waves of dif- dicated by Mr. Crookes's experiments on ferent lengths. He demonstrated that if what he names "electrical evaporation." the electric sparks have a frequency of It was already known that an induction four or five per second, a clean white current, when passing through the platpaper screen is sufficient to stop them; inum electrodes of a vacuum tube, tears but when the frequency of the sparks is off the molecules of platinum from the fifty, or more, the white paper screen sphere of attraction of the wire, and transmakes no perceptible difference. If the ports them to a certain distance. Now, paper is thoroughly blackened with ink on Mr. Crookes, comparing these phenomena both sides, some moderate frequency of a with those of evaporation of liquids, made few hundreds per second is, no doubt, various experiments in order to determine sufficient to practically annul the effect of the "evaporating" power of the electric the interposition of the screen. For dis- stress under different circumstances and charges following each other with frequen- with different substances. He caused cies up to one thousand millions in a water to be transported in this way by the second, a screen of blackened paper is per- electric current; in order to increase the fectly transparent," but if we raise the fre- power of electricity upon metals, he diquency to five hundred million millions, the minished the cohesion of their molecules influence to be transmitted is light, and by heating the metals; and he studied the blackened paper becomes an almost also the relations between the transport of perfect screen."† As to the wonderful the molecules by electric stress, and the electrical effects produced by means of phenomena of phosphorescence.§ One currents alternating with very high fre- feels, especially when remembering the quency, such as they are produced by the speculations of the first half of this cenMontenegrin professor, Nikola Tesla, the tury (chiefly those of Séguin), that a new readers of this review have already been and most promising field is opened by familiarized with them in a preceding these researches; they raise a host of number (LIVING AGE, No. 2496, p. 309). questions relative to the most difficult Many more researches - some of them parts of molecular mechanics. Drahtwellen," in Wiedemann's Annalen der Physik, 1891, vol. xlii., p. 405. Ritter and Rubens in same periodical, vol. xl. 1890. MM. Sarasin and De la Rive having come to the conclusion that the vibrators send out a great number of undulations of various periods, new researches were undertaken by Bjerkness (Archives des Sciences physiques et naturelles, 1891, t. 27, p. 229), and they brought to light the so-called "dampening" of electrical undulations-a question which also was discussed mathematically by Poincare (Archives, t. 25, p. 609), and Perot (Comptes Rendus. anuary 25, 1892). All the gases, many liquids, and many solids (glass, gutta-percha, etc.)- all named dielectrics offer a great resistance to the passage of electricity. A considerable expenditure of work is required for the pas sage of electricity, and the relative amounts of this The same must be said as regards modern research in chemistry. The work now done is of two different kinds. While a numerous army of laboratory workers accumulate heaps and heaps of minute facts, and study the properties of separate chemical compounds without being guided by any general idea, a few chemists devote themselves to the most intricate questions reactions and molecular structure. They relative to the very substance of chemical endeavor to bridge over the gulf between molecular physics and chemistry, and to On some Test Cases for the Maxwell-Boltzmann Doctrine regarding Distribution of Energy, by Sir William Thomson, in Proceedings of the Royal Society, vol. 1., No. 302, p. 79. + Philosophical Magazine, 1890, vol. xxix.; Proceedings of the Royal Society, January 15, 1891. Annalen der Physik, 1892, Bd. 45, p. 28. § Proceedings of the Royal Society, vol. 1., p. 87. conceive the latter as a separate branch of | of this work, and the recent researches of physics and mechanics. But we shall Strasburger, Flemming, Guignard, and postpone the analysis of these endeavors, Fol, while fully confirming the broad gen hoping that some opportunity may soon eralizations laid at the foundation of modbe offered to come to some more definite ern biology, revealed a wide series of new ideas out of the conflicting theories of the facts having a direct bearing upon the present moment. question of heredity, which is so much debated now in connection with Weissmann's views.* IV. WHEN Schwann, closely following upon Robert Brown's and Schleiden's work, published in 1839 his famous "Microscopical Researches," and came to the conclusion that all possible tissues of both animals and plants consist of cells, or of materials derived from cells, it seemed that the primary units - the molecules, so to say-of which all living beings are built up, had finally been discovered. A small piece of structureless, granulated, jelly-like substance- the sarcode in animals and the protoplasm in plants-surrounded or not by a thin membrane, and containing a nucleus, this was the primary unit, giving origin to all the most complex and varied tissues. It appeared, first, from the above-mentioned researches, that protoplasm itself consists of, at least, two different substances; one of them being a minute network of very delicate fibrils, while the other is an apparently homogeneous substance filling up the interstices between the network. Then it became evident that the nucleus which makes a necessary constituent part of cells, has a still more complicated structure, and that it plays a most prominent part in all the phenomena of subdivision of the cells and those of reproduction. It consists of a nuclear plasm, surrounded by a very thin membrane; it contains very often a still smaller nucleolus; and within the nuclear This conception evidently gave a for- plasm the microscope discovers extremely midable impulse to science and to scientific thin threads, or fibres, consisting in their philosophy altogether, the more so as it turn of extremely thin minute granules, or was soon followed by a most important spherules - the whole appearing as a ball discovery which established the close re of thread coiled up somewhat roughly.† semblance existing between the subdivi. This being the usual aspect of the nucleus, sion of cells and the phenomena of sexual a series of modifications begin within it, reproduction in plants and animals. Twen- when the moment comes for a cell to subty-two years later, another still more divide. The nucleolus disappears; the important step was made in the same beaded threads, or fibres, shorten and bedirection, when Max Schultz published come thicker. They take the shape of his memoir, "Das Protoplasm," and minute hooks, and these hooks join toproved that the granular, jelly-like sub-gether (by the tops of the bendings) in one stance of the cells is identical in both the animal and vegetable kingdoms; that it is the very seat of all physiological activity, as it is capable of movement, of nutrition, of growth, of reproduction, and even of sensibility, or, at least, of irritability. Many must certainly remember the effect produced by the broad generalizations based upon Max Schultz's ideas by Haeckel in Germany and Mr. Huxley in this country, in his well-known lay sermon, "The Physical Basis of Life." point, the pole. By the same time the membrane of the nucleus is reabsorbed, and the surrounding protoplasm of the cell penetrates within the nucleus, thus mixing up together with the nuclear plasm. Thereupon a most important change fol Strasburger, Ueber Kern und Zell Theilung im Pflanzenreiche, Jena, 1888; Guignard, in Bull. Soc. botanique de France, 1890, t. 36, and Comptes Rendus, 1891, t. 112, pp. 539, 1074, and 1320; t. 113. P. 917; 1891, Bd. 37, P. 249, and Anatomischer Anzeiger, W. Flemming in Archiv für mikrosk. Anatomie, 1891, p. 78. An immense literature has suddenly grown up upon this subject. Excellent résumés of the whole question have been given in English, up to 1888, by Prof. McKendrick in Proceed. Glasgow Philos. Soc., vol. xix.; and to the end of 1890 by Sir William Turner, in an address, "The Cell Theory, Past and Present,' delivered in October, 1890, before the Scottish Micro + The albuminous matter of which these threads con However, if protoplasm were the seat of physiological activity; if it could move, grow, reproduce itself, and display irritability, was it still to be considered as a "structureless, granulated jelly or slime "?scopical Society (Nature, vol. xliii., p. 11 and sq.) It was a world in itself, and the microscope had to be directed towards the further study of this world. So it was, by Lionel Beale, Schultze himself, Strasburger, and most histologists of renown. Discovery upon discovery was the reward sist received the name of "nuclein," and the threads themselves were named "chromatin fibres," owing to their affinity to coloring matter. The transformations in the nucleus which have just been described received the general name of "karyokinesis," or "nuclear movement." The names, as seen, are simply descriptive. lows. Each of the thickened nuclein | is now formed by both coalesced nuclei, fibres, or threads, splits in its length, and surrounded by a radiation of the fibrils of the number of the threads being thus protoplasm. Then begins what Fol names doubled, one-half of them is attracted"the quadrille of the centres." Each of towards a radiated spindle-figure in one them divides into two half-centres, and all part of the cell, while the other half ar- four move, so that each half-centre of the ranges in the same way in its opposite male cell meets and coalesces with one part. The two radiated figures thus sep- half-centre of the female cell, and the two arate, and only then (if the nucleus sub- newly formed centres become the poles of divides in giving origin to two new cells) a attraction for the spindles of the nucleus. membrane, or parts of a membrane, grow The act of fecundation is thus not a simple between the two. After the separation, coalescence of two nuclei, originated from the fibres either coalesce with their ends, two separate individuals, as was supposed or return in the shape of a ball of thread. before; it also consists of the union of each two of the four half-centres originated in the protoplasm. It is a whole world undergoing a whole cycle of modifications. And yet this is not all. It appears from Strasburger's work The interest attached to these minute that all the cells are not quite similar, but changes is great, on account of their conthat the number of nuclein fibres varies sequences as regards the theory of heredfrom eight to twelve and to sixteen in ity. The observations of Fol, and the various families of plants, the individuality quite analogous observations of Guignard of the types thus seemingly depending as regards plants, would only confirm the upon their number; while Guignard found that with several plants the cells which will be destined, after the division of the mother cell, to become the reproductive organs will always have but one-half of the normal number of fibres (say twelve), while those which are destined to become the vegetative organs will have the full number-say, twenty-four. The former will acquire the full number of fibres only after fecundation. Are, then, the cells differentiated from the first moment of their bi-partition? And what part does the number of chromatin fibres play in that differentiation? Further complications are discovered through the study of the protoplasm itself. It was known some time ago that there are, in the animal cells, two peculiar spots, surrounded by rays of sarcode, which were named spheres of attraction, or directing spheres, or centrosomata, or simply "centres." The same minute centres have now been found by Strasburger and Guignard in vegetable cells also, and it appears that these bodies, essentially belonging to the protoplasm not to the nucleus take a leading part in the phenomena of reproduction. Professor Fol, who carried on his researches with eggs of sea-urchins, saw that when the elements of the male cell have entered the female cell, the centre of the former separates from the top of its nucleus and joins the centre of the latter. Both lie close to one another; then they become elongated and take positions on the opposite sides of the nucleus, which doubts expressed by Sir William Turner in his address before the Microscopical Society, as to the germ plasm being "so isolated from the cells of the body generally as to be uninfluenced by them, and to be unaffected by its surroundings;" and they would give further weight to its restrictions as regards Weissmann's theory of heredity. However, the questions at issue are so complicated and so delicate, that further research is wanted, and eagerly expected by specialists. But what is protoplasm itself? What is this jelly-like matter which exhibits all phenomena of life? Science has not yet given a positive answer to this great question. On the one side, we have the germs of an opinion, shared by some biologists who are inclined to see in protoplasm an aggregation of lower organisms. Thus R. Altmann † and I. Straus ‡ consider that the granulations of protoplasm are the essential and fundamental elements of the organic being. As to the cell, it is not, in Altmann's view, an elementary organism, . but a colony of elementary organisms which group together according to certain rules of colonization. They constitute the protoplasm as well as the nuclear plasm, and they are the morphological units of all living matter. These granules, he maintains, are identical with microbes; their shape, their chemical reactions, their movements, and their secretory functions are similar; but the granules of the pro |