FIG. 69.-The Brain as seen when a Vertical Longitudinal Section has been made through its middle. Av, arbor vitæ of the cerebellum; c, cerebrum; cc, corpus callosum; cq, corpora quadrigemina; f, fornix (between the fornix and the corpus callosum is the septum lucidum); m, medulla oblongata; ma, corpus mammillare; on, optic nerve: pl, pineal gland; pt, pituitary body; pv, pons Varolii; s, soft, or middle commissure. nised since it supports two conspicuous little bodies. One of these (Figs. 69, 70, 71, pl) is called the pineal gland, and projects more or less upwards; the other (Figs. 69, 70, 71, pt) projects downwards and is called the pituitary body. 4. An also very small portion relatively, is d'istinguished by bearing certain small prominences (Fig. 69, cq, and Fig. 70, na and te) placed behind the pineal gland, and called corpora quadrigemina. 5. A rounded mass of finely folded brain-substance, placed at the lower part of the back of the head beneath the hinder portion of the cerebral hemispheres. This is FIG. 70.-Enlarged and Diagrammatic View of a Vertical Section carried through the Corpus Callosum and the parts below. ac, anterior commissure; cc, corpus callosum; cbl, cerebellum; cm, corpus mammillare; f, fornix; fm, foramen of Monro; i, infundibulum; , locus; perforatus medius; mo, medulla oblongata; na, nates; on, optic nerve; pc, posterior commissure; p, pons Varolii; pl, pineal gland; pt, pituitary body; s, soft, or middle commissure; sl, septum lucidum; f, lamina terminalis; te, testes; v, velum interpositum (between it and the fornix is a space enclosed by the folding over of the cerebrum upon the roof of the third ventricle); 3. upper, and 3, lower part of third ventricle; 4, fourth ventricle-between them is the iter a tertio ad quartum ventriculum. called the cerebellum, and when cut through exhibits singular, radiating, tree-like markings, due to the infoldings of the surface of the organ, and called the arbor vita (Fig. 70, av). 6. That part which directly continues the brain into the spinal marrow (Fig. 71, m). It is overlapped by the cerebellum, and contains that portion of the remnant of the primitive nervous canal, which is named the fourth ventricle. This sixth fundamental part of man's brain is called the medulla oblongata. 5. FIG. 71.-Diagram illustrating the progressive Changes that take place during successive stages of the Development of the Brain. 1. The brain in its very early condition, when it consists of three hollow vesicles the cavity of which is continuous with the wide cavity (d) of the primitive spinal marrow (m). The brain substance forms an envelope of nearly equal thickness throughout. 2. Here the first vesicle or forebrain has developed the pineal gland (p) above and the pituitary body, (pt) below. The wall at the anterior end of the first vesicle (or forebrain) is the lamina terminalis (1). 3. This figure shows the cerebrum (cr) budding from the first vesicle, its anterior part (o) being prolonged as the olfactory lobe (the so-called olfactory nerve), the cavity of the cerebrum (or incipient lateral ventricle) communicating with that of the olfactory lobe in front and with that of the first cerebral vesicle (third ventricle) behind. The latter communication takes place through the foramen of Monro. The walls of the three primitive vesicles are becoming of unequal thickness, and the cavity (6) of the middle vesicle (iter a tertio ad quartum ventriculum) is becoming reduced in relative size. 4. The cerebrum is here enlarged, and the inequality in thickness of the wall of the primitive vesicle is increased. The thickened upper part of the wall of the cerebrum is the fornix (). 5. This figure shows the cerebrum still more enlarged, and with a triradiate cavity (1, 1, 2, 3). The fornix has now come to look slightly downwards; dotted lines indicate the downward extension of its anterior part, into the corpora mammillaria. 6. Here the cerebrum is still more enlarged and backwardly extended. The fornix is shown bordering the descending cornu and extending into the temporal lobe (tl) of the cerebrum, which lobe is destined to descend (when the brain is fully developed) so much more that it comes to advance forwards. The fornix borders the margin of the very thin outer wall of the descending cornu, which when torn forms the fissure of Bichat. The bending back of the cerebrum has now almost enclosed (between the fornix and the velum) the space (x) which in Fig. 4 is widely open, making what is morphologically called the outside of the brain come practically to be in its very centre. a, fore-brain; b, mid-brain; c, hind-brain; cb, cerebellum; cr, cerebrum; d, cavity of the medulla;f, fornix; /, lateral ventricle; m, medulla oblongata; ma, corpora mammillaria; o, olfactory lobe; P, pons Varolii; pl, pineal gland; pt, pituitary body; 4, corpora quadrigemina; r, crura cerebri; t, lamina terminalis; tl, temporal lobe of the cerebrum; x, space, enclosed by the extension backwards of the cerebrum; 1, anterior cornu of lateral ventricle; 2, its middle or descending cornu; 3, its posterior cornu. In the earliest conditions of the human brain the resemblance is much more marked and obvious; it is later that the correspondence between the brain of the frog and that of man becomes so disguised through the unequal growth of different portions of the organ in the human brain as it advances in its growth and development. The same six successive portions, however, exist in each. 1. In the frog the olfactory lobes acquire a much larger relative size, and they retain permanently an internal cavity which exists only transitorily in man. 2. The cerebral lobes (or hemispheres) exceed those just noticed but are insignificant indeed, when compared with the corresponding human structures. They may, however, be more insignificant than in the frog, as, for example, in the lamprey, where they are actually smaller than the olfactory lobes. In that the cerebral lobes of the frog each contain a cavity (the lateral ventricles) they have a character which is constant in all animals above fishes, they open by a common aperture (foramen of Monro) into the cavity of the next brain segment behind. 3. This third segment retains a great relative magnitude compared with that of man. 4. The fourth segment, however, consisting of the optic lobes, attains a still further relative development, though consisting only of two bodies instead of four, but these contain a cavity not found in the corpora quadrigemina of the human brain. 5. The fifth segment, the cerebellum, is very small, and It has been already said, that in man and the higher animals there are nerves supplying the orbital muscles and different parts of the face. The eyeball in man is moved by six little muscles, four straight, (the recti) and two oblique, one being the upper, the other lower, oblique. Now a nerve called the third, because it follows the first two (olfactory and optic) goes from the brain to all the orbital muscles except the upper oblique and the outer rectus. Another nerve, the fourth, proceeds to the upper oblique muscle only. The fifth nerve is a very large one, and supplies the nose, tear-gland, eyelids, upper and lower jaws, tongue and teeth. The sixth nerve is a very small one indeed, being exclusively applied to the outer rectus muscle of the orbit. The seventh nerve is, in part, the auditory nerve in part it sends fibres to the face. The eighth nerve is a very complex structure, and consists of, at least, three nerves united together, all arising from the medulla oblongata. It sends branches to the parts about the throat, as well as to the organ of voice, to the lungs, the stomach and the heart. The nerves of the frog exhibit certain intermediate conditions like those we have seen to exist in various other parts of its anatomy. In the higher vertebrate animals, as in Man, the 3 5 FIG. 72.-Brain of Bull Frog in various views. 1, Dorsal view. 2. Lateral view; 3, Transverse horizontal section showing the cavities of the olfactory cerebral and optic lobes. 4, Longitudinal section a little to the left of the median line. 5, Longitudinal section in median line. The corpus striatum, c, is here exposed to view and also a body, g, within the optic lobes. 5, Longitudinal section in median line. In all five figures:-1, Olfactory nerve; 2, optic nerve; 4, auditory nerve; a, olfactory lobe; b, cerebral lobe; c, corpus striatum; d, optic thalamus; e, pineal gland;, pituitary body; g, optic lobes; h, cerebellum. smaller than the same part in animals both higher and lower in the scale; indeed, in the frog class, this organ may be said to be at its minimum. When cut it exhibits no trace of an arbor vitæ, This fact has a special interest as bearing on alleged functions of this portion of the brain. It has been asserted by some that the cerebellum ministers to the sexual functions, by others that this part coordinates and directs locomotive movements, and, quite lately, that it is related to movements of the eyes. The first two of these hypotheses seem to be completely overthrown by our frog. In the first matter there is any thing but a deficiency of energy and activity, and as to the second, many reptiles are less active and continuous than the frog in their locomotive efforts. As to the third hypothesis, it should be remembered that the eyes of the Frog are large and very moveable, as also that they require a power of ready adjustment to enable the animal to secure its insect prey. 6. The sixth and last segment of the brain, the medulla oblongata, is also relatively large, and is exposed to view through the rudimentary development of the cerebellum which, as has been said, overlaps it in man. C.h. 2012 FIG. 73-The Muscles of the Eyebails, viewed from above and from the outer side. R.S., the superior rectus; Inf.R., the inferior rectus; E.R., the external rectus; In.R., the internal rectus; S.Ob., the superior oblique; Inf.Ob., the inferior oblique; Ch, the chiasma of the optic nerves (II.); III., the third nerve, which supplies all the muscles except the superior oblique and the external rectus. muscles which move the eye-ball are supplied by three distinct nerves termed respectively the 3rd, 4th, and 6th. The 5th nerve being a very large and complex one, sending branches to various parts of the head and its organs. This Now in the frog there is no distinct 6th nerve, it being replaced by an extra branch of the 5th nerve. modification, however, is but one step towards a condition which obtains in the Mud-fish (Lepidosiren), when all these three nerves are quite blended with one division (the Ophthalmic) of the fifth nerve. Again in the higher Vertebrates, as in Man, the 8th nerve is a very large and complex one, and distributed as in him. It is also so distributed in the adult frog. In the tadpole, however, this nerve shows a very different arrangement. After issuing from the skull this nerve sends a branch down the outer side of each branchial arch and then gives off a very long one, which extends laterally, i.e. along the side of the body and tail. Nothing like this exists in any Beast, Bird or Reptile, but when we come to the class of Fishes we encounter a precisely similar state of things. Here we find the eighth nerve sending a branch to each branchial arch, and giving off a great nerve proceeding along the side of the body and tail, and on that account named the nervus lateralis. ST. GEORGE MIVART (To be continued.) THE INDUCTION TUBE OF W.SIEMENS A TRANSLATION from a French periodical, La Na ture, of an article on " Tubes for silent electrical discharges," appears in NATURE of Jan. 29 (vol. ix. p. 244). After referring to the action of the electric spark upon oxygen gas, the author of the article continues: "For the purpose of more easily obtaining ozone, M. Houzeau has recently constructed an apparatus worked by a Ruhmkorff coil, in which there are no longer sparks, but only dark discharges-effluvia-far more efficacious in the production of modified oxygen." Again, it is said, that M. Houzeau "has recently devised an apparatus for the preparation of ozone, which is spreading rapidly among the laboratories, and which has already yielded very remarkable results." A description of the apparatus is then given; further on, it is said, that "M. Houzeau is not the only one who has made use of the tubes whose structure he has made known, but that M. Boillot, a writer, it appears," well known to the readers of the Moniteur, "has made some further propositions about them; and lastly, that M. A. Thénard" (whose investigations constitute the main subject of the article) "has brought to bear on the construction of the tubes a further modification which | makes them still more efficacious." A description and drawing of the apparatus of M. A. Thénard is given. Those who are unacquainted with the facts of the case will be surprised to learn that the invention thus publicly announced, although, doubtless, in principle deserving of the highest praise, was not made either by M. Houzeau, M. Boillot, or M. A. Thénard, but is simply a somewhat clumsy form of the Induction-tube devised by W. Siemens, which is described in his "Memoir on Electrostatic Induction," contained in Poggendorff's Annalen, for 1857 (vol. cii. p. 120). This Induction-tube is one of the most remarkable, as well as simple instruments, of chemical research which has ever been devised; enabling us, by the action of electricity, to effect changes in the composition of gases which may be compared with the chemical changes effected in liquids by the agency of the voltaic battery. A few words in explanation of the instrument may interest the readers of NATURE. The simplest form of induction-apparatus consists in two thin glass plates, of which one side is coated with tin-foil, and which are so arranged that the uncovered surfaces are parallel to one another, and separated by a uniform, narrow interval of about one or two millimetres filled, say, with air. If this apparatus be charged with electricity by a sufficiently charged Leyden jar, at the moment of the charge the air between the plates becomes luminous, and the same appearance is presented when the apparatus is discharged. To produce this effect, however, the apparatus must be charged beyond a certain limit, determined, in each case, by the special arrangement of the apparatus and the materials employed in its construction. Now, if the two plates of tin-foil be respectively connected with the terminals of a powerful Ruhmkorff's coil, the apparatus is successively charged with electricity and discharged; these operations being alternately repeated in such rapid succession that the air, in the interval between the plates, appears permanently luminous. We have, moreover, evidence of the occurrence in this interval of chemical changes determined by the electric action, in the odour and characteristic properties of ozone which may be recognised in a current of air or oxygen compelled to pass between the plates. The conclusion drawn by Siemens from this experiment is, that the electric polarisation of the particles of a dielectric cannot be carried beyond a certain point; and that if it be attempted to accumulate electricity in the apparatus beyond this point, the excess of this tension or polarisation appears in the form of the dynamical phenomena occurring between the plates, Now it is evident that in this If the reader will be at the of Siemens he will be satisfied of At the same time if the 6.a ACTUAL SIZE in the article translated in NATURE, B. C. BRODIE RECENT RESEARCHES ON TERMITES AND THE accompanying letter, just received from Fritz "For some years I have been engaged in studying the natural history of our Termites, of which I have had more than a dozen living species at my disposition. The several species differ much more in their habits and in their anatomy than is generally assumed. In most species there are two sets of neuters, viz., labourers and soldiers; but in some species (Calotermes Hg.) the labourers, and in others (Anoplotermes F. M.) the soldiers, are wanting. With respect to these neuters I have come to the same conclusion as that arrived at by Mr. Bates, viz. that, differently from what we see in social Hymenoptera, they are not modified imagos (sterile females), but modified larvæ, which undergo no further metamorphosis. This accounts for the fact first observed by Lespès, that both the sexes are represented among the sterile (or so-called neuter) Termites. In some species of Calotermes the male soldiers may even externally be distinguished from the female ones. I have been able to confirm, in almost all our species, the fact already observed by Mr. Smeathman a century ago, but doubted by most subsequent writers, that in the company of the queen there lives always a king. The most interesting fact in the natural history of these curious insects is the existence of two forms of sexual individuals, in some (if not in all) of the species. Besides the winged males and females, which are produced in vast numbers, and which, leaving the termitary in large swarms, may intercross with those produced in other communities, there are wingless males and females, which never leave the termitary where they are born, and which replace the winged males or females, whenever a community does not find in due time a true king or queen. Once I found a king (of a species of Eutermes) living in company with as many as thirty-one such complemental females, as they may be called, instead of with a single legitimate queen. Termites would, no doubt, save an extraordinary amount of labour if, instead of raising annually myriads of winged males and females, almost all of which (helpless creatures as they are) perish in the time of swarming without being able to find a new home, they raised solely a few wingless males and females, which, free from danger, might remain in their native termitary; and he who does not admit the paramount importance of intercrossing, must of course wonder why this latter manner of reproduction (by wingless individuals) has not long since taken the place through natural selection of the production of winged males and females. But the wingless individuals would of course have to pair always with their near relatives, whilst by the swarming of the winged Termites a chance is given to them for the intercrossing of individuals not nearly related. I sent to Germany, about a year ago, a paper on this subject, but do not know whether it has yet been published. "From Termites I have lately turned my attention to a still more interesting group of social insects, viz., our stingless honey-bees (Melipona and Trigona). Though a high authority in this matter, Mr. Frederick Smith, has lately affirmed, that "we have now acquired almost a complete history of their economy," I still believe, that almost all remains to be done in this respect. I think that even their affinities are not yet well established, and that they are by no means intermediate between hive- and humble-bees, nor so nearly allied to them, as is now generally admitted. Wasps and hive-bees have no doubt independently acquired their social habits, as well as the habit of constructing combs of hexagonal cells, and so, I think, has Melipona. The genera Apis and Melipona may even have separated from a common progenitor, before wax was used in the construction of the cells; for in hive-bees, as is well known, wax is secreted on the ventral side in Melipona on the contrary, as I have seen, on the dorsal side of the abdomen; now it is not probable, that the secretion of wax, when once established, should have migrated from the ventral to the dorsal side, or vice verså. : "The queen of the hive-bee fixes her eggs on the bottom of the empty cells; the larvæ are fed by the labourers at first with semi-digested food, and afterwards with a mixture of pollen and honey, and only when the larvæ are full grown, the cells are closed. The Meliponæ and Trigonæ, on the contrary, fill the cells with semidigested food before the eggs are laid, and they shut the cells immediately after the queen has dropped an egg on the food. With hive-bees the royal cells, in which the future queens have to be raised, differ in their direction from the other cells; this is not the case with Melipona and Trigona, where all the cells are vertical, with their orifices turned upward, forming horizontal (or rarely spirally ascending) combs. You know that honey is stored by our stingless bees in large, oval, irregularly clustered cells; and thus there are many more or less important differences in the structure, as well as in the economy, of Apis and Melipona. "My brother, who is now examining carefully the external structure of our species, is surprised at the amount of variability, which the several species show in the structure of their hind legs, of their wings, &c., and not less are the differences they exhibit in their habits. "I have hitherto observed here 14 species of Melipona and Trigona, the smallest of them scarcely exceeding 2 millimetres in length, the largest being about the size of the hive-bee. One of these species lives as a parasite within the nests of some other species. I have now, in my garden, hives of 4 of our species, in which I have observed the construction of the combs, the laying of the eggs, &c., and I hope I shall soon be able to obtain hives of some more species. Some of our species are so elegant and beautiful and so extremely interesting, that they would be a most precious acquisition for zoological gardens or large hot-houses; nor do I think that it would be very difficult to bring them to Europe and there to preserve them in a living state. "If it be of some interest to you I shall be glad to give may observe you from time to time an account of what I in my Melipona apiary. "Believe me, dear Sir, &c., N MARS* "FRITZ MÜLLER" In the previous article were the previous article were mentioned some of We are induced to add a few further remarks, from their general applicability. The delineation of the heavenly bodies, he says, is always a very difficult task, especially when, as in the case of Mars, we have to deal with features more or less indistinct, delicately and gradually shaded. With the most powerful telescopes the disc is but small; and on it we find a mass of ill-defined and frequently very feeble spots, which require close attention for their disentanglement, and it is hard to obtain a clear conviction as to the outlines and shadings that have to be drawn. The difficulty is much increased by the inces * Continued from p. 289. sant undulations of the air; and in the seldom-recurring moments of stillness so much under good circumstances is visible, that even the best artist cannot draw it all in half an hour, a period during which usually there are but a very few tranquil glimpses, and after which the planet will have materially changed its aspect from rotation. Even were it easier to distinguish what is actually visible, it requires great practice to represent it faithfully; and whoever has had personal experience of the difficulties of such designs will have but a limited confidence in the various portraits or the supposed changes that they represent. As a further illustration of these difficulties he refers to the representations of the Orion nebula by Rosse, Lassell, Secchi, and Liapounov (he could have added Herschel II.); or the portraits given by Bond, and others, of Donati's Comet. He might have cited, had he known of it, Prof. Young's remark as to the solar corona (where, however, these difficulties are heightened by the excitement of the moment), that "the drawings made by persons standing side by side differ to an extent that is sometimes really ludicrous, and has induced more than one astronomer who had not himself seen an eclipse, but judged only from the written accounts and sketches, to declare his belief that this whole outer corona is a mere subjective phenomenon.” would be inconsiderable, while the solar image at the distance of the Earth would be too minute, in all probability, to be visible. This reasoning would seem fairly to hold its ground against that of the Leiden astronomer, who does not believe that seas so looked upon would show such innumerable gradations in tone, or be so invariably ill-defined at their edges, while the same telescope gives perfect sharpness to the polar snows. He goes in fact so far as to say that if we may form any conclusion from their aspect, it is, that they cannot resemble seas such as our own. But as to distinctness of boundary, his experience is not accordant with that of other excellent observers, especially Lockyer, who remarks that "the effect of a cloudless and perfectly pure sky both here and on Mars appears to be, that the dark portions of the planet become darkest and most distinctly visible; the coastlines (if I may so call them) being at such times so hard and sharp that (as has been mentioned by Mr. Lassell) it is quite impossible to represent the outlines faithfully." A more natural inference, it seems to the writer, would be that these fluid masses contain large areas of very slight depth, that the edges are in many places very shelving, and that possibly they may be the more transparent from the absence of salt. Other astronomers, Kaiser tells us, but without mentioning their names, have reversed the idea, and thought the bright parts to be seas, but they do not thus escape his objections on the score of definition, nor account for the dusky tracts which some of the great bright expanses contain. He has perhaps got hold of a more substantial difficulty in the aspect of the north polar region, where the white spot is often encompassed by a widely-extended dark zone with many gradations of tint. The width of this belt, very great when foreshortening is taken into account, is no doubt variable Beer and Mädler ascribed it to the non-reflective power of the damp surface bared by the rapidly melting snow. On the whole, when Kaiser considers that nothing is established with certainty but the existence of an atmosphere and the connection of the polar spots with the seasons, we hesitate to follow him; and we should prefer the conclusion of Phillips, adopted by Lockyer, that "over a permanent basis of bright and dusky tracts, a variable envelope gathers and fluctuates, partially modi The justice of Kaiser's remarks will readily make itself felt, but they do not exhaust the subject; something may perhaps be added as to the "personal equation" of vision. Independently of mechanical defects in the eye, there are inaccuracies of perception; and even if the rays have kept an uninterrupted and undeviating course to the retina, they do not always produce corresponding impressions on the mind. Whatever may be the cause, we frequently meet with defects in the sense of form, or proportion, or inclination, or even the presence of features which are not the immediate objects of attention. Comparisons of size are often very erroneous; craftsmen well know the meaning of a true eye;" and the expression "I did not see it," is constantly employed with reference to a thousand objects whose representation on the retina is all the while unquestionable. It is in these respects that celestial photography is invaluable as recording everything and putting everything in its proper place; but photography, as Kaiser observes, isfying the aspect of the fundamental features, and even in inapplicable to the light of Mars. Another point, too, might have admitted of notice. Although we may certainly, with him, be baffled in reconciling Rosse and Lassell, we may bear in mind, as regards the comparison of larger and smaller instruments, Dawes's important remark to the effect that a certain relative proportion of light and power may be essential to the visibility of some classes of difficult objects. Without subscribing implicitly to the whole of Kaiser's views, some of which admit of doubt-as, for instance, when we contrast his assertion that the spots are never sharply defined, with the clearness and keenness of outline occasionally recorded by Lockyer and others we may well admit their general accuracy. But we find it more difficult to accompany him in his inferences as to the planet's physical constitution. The earth-light upon the moon having been found by Schröter more conspicuous when it proceeded from the hemisphere of our globe containing the largest amount of land, Kaiser implies that it has hence been inferred that (as it is difficult for us not to imagine other planets constituted like our own), the brighter and darker portions of Mars are equivalent to land and water. Whether such an opinion may have been arrived at in this circuitous way or not, it seems highly probable without any reference to lunar appearances. The eminently absorptive power of water is well known; even a thickness of seven feet will, it is said, diminish the incident light by one-half; and below 700 feet it is quenched in unbroken darkness; and the quantity of diffused light reflected from its surface some degree disguising them under new lights and shades, which present no constancy, a thin vaporous atmosphere probably resting on a surface of land, snow, and water.” A more protracted course of observation may possibly modify in some way this result, but so far as past investigations extend, we may say that nothing has been detected inconsistent with it. Could we be actually transported to that far distant surface, we should probably find much to astonish us that we cannot so much as conjecture here; it was a sound remark of Schröter's that unity in variety is the universal character of creation; and the spectroscope of Huggins has already in this instance confirmed it by the detection of absorptionlines the cause of which is utterly unknown. Our future inquiries should be conducted in that impartial spirit which is equally ready to admit the indications of discrepancy and of resemblance, and which is more anxious to ascertain facts than to seek their premature elucidation. We have as yet read but a part of the inscription on that golden shield: some of it has probably been deciphered correctly; how much of the remainder may give way we know not; but the whole, it will never be given to us to understand. The extensive researches in which Dr. Terby of Louvain has for some time been engaged, and in which he has shown unwearied diligence and perseverance, if embodied, as we trust they will be, in one comprehensive result, will give material assistance in disentangling and concentrating our present scattered and discordant materials, and we may look forward with hope to the very |