« ΠροηγούμενηΣυνέχεια »
sides of the intestines. It has a proboscis, and around this are capable of reproducing its species. Most of these cystoid two rows of hooks, which point backward, so that when the animals, when in the cystoid or bladder-like state, inhabit the animal plunges its proboscis into the soft mucous coat it cannot soft structure of herbivorous or grain-feeding animals, while be pulled away, and hence holds its position, notwithstanding when they arrive at the cestoid or tape-worm condition they are the continued transmission of food and the constant motion of found in the carnivorous animals which feed upon their former the alimentary canal by which it passes forward its contents. hosts. It has been shown that the Cysticercus fasciolaris of the Besides these, four suckers are situated below the hooklets on liver of a mouse becomes the Tania crassicollis (the thick-necked the rounded head. An attenuated neck gradually enlarges as it tapeworm) of the intestines of the cat, and the Cysticercus pisiproceeds downwards, and, at a little distance from the head, formis (the pea-shaped bladder-tail) of the rabbit becomes the closely set and fine constrictions are observed, which become Tænia serrata (notched tapeworm) of the dog. In the case of the larger and more especially longer as we trace them downwards species we have been describing, the host of the larva is usually towards the tail-end. These constrictions become also more the pig, and the host of the adult worm is man. As might be and more definite and deeper, dividing the animal into segments, expected, it is found that the Tænia solium infects those most which, being longer than wide and very flat, look like a series of who are especially fond of ill-cooked sausages. In Germany oblong cards.
this unfortunate taste for nearly raw pork has produced the In each of these segments & complete set of reproductive most harmful results, not only by introducing this worm, but organs, both male and female, are found, and each in course of also another called Trichina spiralis, a worm of much higher time produces an immense brood of eggs. When this condition organism, and belonging to an order to be referred to hereafter. has been arrived at, the segment drops off and crawls about, When the flesh containing the encysted entozoa is being digested making its escape from its host, and finally bursting from the by the animal who has been unfortunate enough to swallow it, increased growth of the contained eggs, it scatters an immense the digesting operation goes on not only so far as to liberate the multitude of germs. At a first consideration, one would have creature, but also to dissolve away the bladder which encloses thought that these germs, cast forth into the world, and dependent the head. Then the creature, like the liberated genius in the for development upon their admission to other hosts, would have “Arabian Nights," begins to take revenge on its liberator for its but little chance of complete life; and this is no doubt true with long imprisonment. It fixes itself by its hooks and its suckers regard to each single germ. In this case, however, Nature makes to the walls of the intestines, and its tail grows and becomes up by multitude for efficiency. If we consider that each tape segmented as before described. As compared to the immense worm has many hundred segments or joints when found in the length and size of the chain of segments, the head is ridiculously interior of man, and that these joints are continually renewed small; and thus the simile of the genius, who, when liberated from above as they fall away, and that each segment contains from his bottle, assumed such vast and formidable dimensions, thousands of ova which are cast into various situations-into is not inappropriate to the rapid development which follows the garbage, water, etc.—it is not wonderful that some are taken liberation of this worm from its cyst. into the interior of some suitable animal.
The effect upon the human system occasioned by a tapeworm These animals, being constantly provided with digested food is extremely distressing. The patient suffers not only from loss which has been elaborated by their hosts, do not need any food of appetite, emaciation, and lassitude, but the sympathetic canal of their own to digest aliment, but absorb it when already nervous system is affected so as to produce convulsions and dissolved through the walls of the body. In fact, their stomachs, epilepsy. Distressing, however, as these effects are, they are go to speak, are external, and correspond to the skin of other not so fatal as are those produced by the presence of the im. animals. Running along each side of the animal is a narrow mature form, because the adult worm is confined to the intestines, duct. Cross-branches unite the two ducts, one to each segment, and is thus, so to speak, in a situation external to the body, while and run across at the part farthest from the head. These two the larvæ, as we have seen, penetrates into all parts of the body, lateral canals were long considered as the alimentary system of and their presence is more or less injurious as they take up their the animal; but it was found that it had no opening forward abode in the more or less vital organs. If they find their way to that is, it was without a mouth-and although there is an open a position under the skin or in the muscles, they are comparaing at the other end of the body, yet it is now considered to be tively harmless; but if they penetrate the eye or the brain, the atrial system corresponding to the water-vascular or ambula they occasion pain and sometimes death. cral system which we have described in the Echinodermata. In tracing the circle of life of the Tænia, we find it runs
The egg with its contained embryo being swallowed by some through all the forms named, in the following order :animal, the latter does not remain in the food canal and become 1. The egg. developed into a tapeworm, as might have been supposed, but 2. The embryo, actively travelling by a six-hooked boring immediately that the coatings of the egg are dissolved away, the apparatus. embryo, which is armed with six boring-hooks, makes its way 3. The resting larva, consisting of a head enveloped in a through the walls of the alimentary canal, and traverses the terminal bladder. body in any direction until it reaches some structure suited to it, 4. Immature tapeworm liberated from its bladder. and there it rests and becomes more fully developed. The deve 5. Segmented and sexually mature tapeworm. lopment is commenced by the formation of a bladder which is 6. Free segment, called a proglottis, from its likeness to the proper to the animal, while the soft organ in which the parasite tip of the tongue. is lodged forms a self-defensive cyst around this of common This creature belongs to the sub-class Anenterelmintha, which (areolar) tissue. Thus the creature is snugly ensconced in a is distinguished from the sub-classes to which the other anima cavity, through the walls of which the liquids penetrate, and are of the class belong, by having no alimentary canal of any kind. absorbed by the bladder-like animal. By the aid of this This animal, in common with all belonging to this sub-class nutriment fresh changes occur with the growth of the larva. is entirely nourished by absorption, and for this reason we have Thus on one side of the interior of the bladder a round body taken the tapeworm as the type of an entozoon. grows and so projects into the cavity, and in this the head and The animals of the sub-class Sterelmintha differ from these neck of the future perfect worm are formed. On this head having an alimentary canal channelled out in the substance of the circles of hooks and the suckers are developed, so that the an otherwise solid body. Our best English writer on the Entozoida examination of the larval form when at an advanced stage will Cobbold (whose books should be rend by those who wish for * enable the examiner to detormine to which species the creature more intimate acquaintance with the class), takes the Distoma con belongs. When this process is completed, the larva has reached | junctum, which he found in the intestines of the American red a stage beyond which it cannot become more developed unless it fox, as a type of the sub-class. The animal belonging to changes its position, and this change of position is not an active sub-class, with which we are unfortunately best acquainted, ..5 but a passive one. Hence multitudes of these creatures probably the liver-fluke, which occasions the disease called the top mu die and become disintegrated without ever attaining the perfect sheep. This creature is found abundantly in the liver of sheep form. Those, however, whose life-circuit becomes complete, are affected. Sometimes as many as a thousand have been found transferred to the stomach of a carnivorous animal by the flesh a single liver. The animal is of considerable size, measurua in which they are lodged being devoured. Thus the animal has from to 1 inch in length, and about 1 inch in breadth. It is! two different hosts, one of which entertains it in the immature and shaped like a little sole. Its anterior extremity is exter condition, and the other when it becomes perfect and sexually | into a nipple-shaped projection, at the end of which i
sucker, which is perforated by the mouth of the animal. Another to the annelids or true worms. Doubtless they lie between these sucker of larger size is situated on the under side of the body, classes; but whether they are so much more nearly associated at about a quarter of an inch from the mouth. This is similarly with the first-named as to be properly placed with them in a constructed, but is imperforate, and does not communicate with separate sub-kingdom, called Annuloida, may be doubted by any internal organ. Locomotion, so far as it is needed to this some. animal, is effected by these suckers, which can be alternately The class may be thus divided into sub-classes and orders:attached, and also by the general flexibility of the body, which
Sub-class, has a muscular layer beneath the epidermis. The mouth leads
(1. Cestoda = tapeworm. down into a short gullet, below which the alimentary canal
I. Anenterelmintha 2. Acanthocephala = thorn. divides into two main trunks, which run down to the tail-end of
headed worm, the animal, giving off blind branches in a way best explained by
3. Turbellaria : non-parasitic.
II. Sterelmintha the engraving. There is no anus, and this perhaps is not needed,
4. Trematoda = flukes. on account of the highly organised food which the animal
(III. Cælelmintha 5. Nematoda = round worms. ingests. The fluke, however, readily ejects the food from its branched stomach, by curling itself up like a little strip of heated parchment, and thus squeezing it out. Another system
LESSONS IN MUSIC.—XI. of vessels has a single opening towards the tail of the body, WHILE our pupils are advancing in their own practical study and runs forward, giving off branches on either side, and then, of the three principal notes of the scale, in connection with the when it has arrived at a distance of about one-third of the tunes given in this and the following lesson, we shall usefully length of the animal from the oral sucker, it splits into three occupy our time in reviewing and making the more sure some branches. This system correspon 3 with the water-vascular of the steps already taken. One of the chief anxieties of the system of the Tania.
art of teaching is that of ascertaining where lie the real diffiThis animal is hermaphrodite, that is, it has both male and culties of our pupils. This we are enabled to do by means of female organs. The development of these creatures is peculiar. the correspondence with which we have been favoured. Most It is supposed that when the animal containing matured eggs is of the mistakes of our pupils have arisen from careless reading voided from the sheep, it reaches some moist place or pool of or from a forgetfulness of the pledge to which at first we sought water, and deposits its eggs, which emit a larva which swims to bind them. This was the pledge: “We have only two about by cilia, and has a single X-shaped eye. This larva fixes things to ask of you: the first, that you will be content to learn on some fresh-water snail and penetrates its skin, and when it one thing at a time, instead of being impatient for knowledge has arrived at the interior, is transformed into a large bag or not at the moment helpful—perhaps, just then, only confusing nurse, containing in its interior many tadpole-shaped animals to you; the second, that when something is set before you to with long tails, called cercarice. The cercariæ once more escape, be done, you will really do it, instead of supposing it to be done, not only from their foster-parent or nurse, but also from their and going on; for only by doing we truly understand.” But molluscous host, into the surrounding water, and it is probable without judging our friends too nicely, we will try to meet their that they are imbibed with the water by sheep, and then pene- difficulties. Those difficulties relate to the “modulator,” the trate to the liver, causing the rot. In accordance with these | “pattern," and "the movable Don.” suppositions, some of which have been observed not in the liver “ What I want,” says one of our correspondents," is to be Auke, but in nearly allied species, it is found that sheep fed on able to measure to the eye the exact interval the voice is taking." dry land or on the great salt-water marshes are comparatively It is just for this purpose that the modulator is provided. The free from rot, while those fed up in fresh-water marshes are ordinary staff of five lines and four spaces does not measure peculiarly subject to it. The disease associated with these to the eye the exact interval the voice is taking, because it fails creatures is of considerable economic importance, as in some to show pictorially the places of the “semitones” (small steps) years it has been reckoned that between one and two millions of the scale. This is, however, a point of vital importance to of sheep have died of the rot in Britain alone.
the learner, and one which should be kept constantly before his Besides the flukes there is another sub-class of Helminthozoa, eyes. Hence the necessity of some such scale as the modulator called Cælelmintha, or hollow-bodied worms. These have ali- offers. The modulator also possesses the advantage of showing mentary canals of the same type as the higher animals, being not only lines or marks for the notes, but the names of the notes tubes within tubes. The alimentary canal consists of a strong themselves. Our pupils have to use only the middle column at eesophagus, a dilatation or bulb containing a comminuting appa- present. In order thus to measure to the eye the interval the ratus, or gizzard, and then a stomach continued into an intestine. voice is taking, our pupil must not be constantly looking from These creatures are not hermaphrodite, but the individuals are the book to the modulator and from the modulator to the book. male and female. Some of these animals are not parasitic at all, He must first learn a few notes of his tune "by heart," and and some of them only under certain circumstances. Thus, there then sing them from the modulator alone; and so on till he can is found in the tropical regions of Asia and Africa an intoler point the whole tune from memory, and without the book. able pest, called the Dracunculus Medinensis. This trouble. Thus, if he is learning Exercise 5, let him just read and repeat some parasite is always the female, and it gains access to the to himself “DOH, SOH, ME, DOH," several times over. Then let body from water through the skin, and then grows and emits him, laying aside his book, turn to the modulator, and sing these its brood, to the great annoyance of its host, often occasion-notes while he points to them. Next let him learn to "point and ing death. When it reaches its full size it is many feet in sing,' without book, the phrase “ME, ME, DOH" in the same length, though only of an inch in thickness. It will migrate manner, and after that the whole exercise. Very extensive beneath the skin from one part of the body to another. Some experience in teaching has made us feel increasingly the im. have supposed that these animals were the fiery serpents which portance of requiring the pupils thus to "see," and themselves attacked the Israelites in the wilderness. The only remedy point out the intervals they sing on a perfect scale like the seems to be to cut down to the worm, and having got hold of modulator. It is only by this painstaking that a real knowledge one end this is wound round a piece of stick. When thus of interval is gained. If the pupil will begin at the beginning secured the stick is left for a day or two, and then more of the and faithfully pursue this plan, we can promise him that long worm's body is drawn out, and a further winding takes place, before he has reached the present lesson he will have attained and so on until the whole is extracted entire. If the worm such a facility in “pointing from memory on the modulator” as be broken, as it swarms with eggs, all the bad effects take will make the exercise quite a delightful one to him. “Oh," place which would necessarily ensue if the creature were left said a little girl to her mamma, as they were travelling in a unmolested.
railway train, and a stranger opened a number of the POPULAR The class Helminthozoa show, by their development within EDUCATOR, "Oh, mamma, there's a modulator !” “What do you ciliated larval forms of utterly different form from the adult know of a modulator?” said the stranger. “Oh! I know someanimal, by the possession of a water-vascular system, and a thing," was the answer, and the happy child soon convinced the radial structure of their head-organs, an affinity for the Echino- stranger that she “knew something” by singing and pointing" dermata. On the other hand, their elongated and transversely as she sang several of the tunes she had learnt at school. striated or segmented forms, as well as the position of the Upwards of seven thousand pupils in the United Kingd Beanty representatives of the nervous system, show an approach during the past year (1867) took “certificates of profici
KEY-BOARDS OF THE GERMAN CONCERTINA.
necessary. If you are already acquainted with an instrument, such an instrument, and can sing it perfectly without the instruwhatever it is, use that. Only let us warn you not to sing with ment, exercise himself in striking the sound G, and raising a chord your instrument that is, to use it as a pattern,” not as a (DOH, ME, SOH) upon that, without a pattern. Next, let him "leader”—to make yourself independent of the pattern as soon raise a chord on the sound D, next on the sound A, next on E, and as possible, often endeavouring to do without it, and to trust next on B, in the same manner as before. After this let him try more and more to your own perception of the mental effect of to sing, not only the chord, but the whole scales of G, D, A, and E. notes, as developed in our lessons; for instruments may be out Many will be able to do this ; and they, when they have learnt of tune, and some of them-the piano and organ for instance, their tune by pattern in the key of c, will easily manage to pitch are systematically (to however small an extent) imperfect in the proper key-note, raise the chord upon it, and afterwards sing tune. The flatness of the fifths on the piano, for instance, are the tune itself in the key for which it was written. We should, very obvious. The fifth note in the scale (son) should be bril. however, recommend our pupils to purchase the glass-harmoliant and trumpet-like in its effect. The pupil's knowledge may nicon with two octaves. Let them mark it with the syllables, thus correct the slight inaccuracies of his instrument. We and use it in the same way as that with one octave. For a slight have been at some pains to make inquiries with a view of re- additional expense, any maker of these instruments would concommending some cheap instrument to our pupils with which struct one for you tuned in the key of G, or in any other key fou they may set the pattern. We shall in this article describe may desire. In that case, you must paste your doh upon the two of the most accessible," the glass-harmonicon" and "the glass marked G, RAY upon that marked A, and so on. With these German concertina."
two instruments you would be able to play most of the tunes The glass-harmonicon is a well-known and cheap instru- very fairly. You would still lack the so-called "accidentals, ment, in which the sounds are produced by striking with a | not yet explained in our lessons. light hammer on small plates of glass. These are of different The German concertina consists of two hand-boards with
and are placed in a row, fastened to two slightly bellows between. The metallic tongues by which the sound is
tapes, as in the illustration given above. The produced, and the machinery by which the little pegs, when
pressed by the hand, direct the current of air upon them, are this will give him DOH. Next let him draw the bellows, holding all concealed. We have drawn the hand-boards as though they down the same peg: this will give him ray. Next, holding were made to face us. The right hand is passed through down the fourth peg, let him press and draw : this will give the strap so that its thumb can command the valve at the side, him ME and FAH. In the same manner the fifth peg will give and its fingers the pegs by which the notes are produced. In him son and LAH. But now, in order to continue ascending a similar manner the left hand is passed through the other the scale on the right-hand board, he must no longer press and strap, so that its fingers can press the pegs of the other board. draw, but draw and press. A similar alteration in the recur. You can thus open or close the bellows with the hands while the rence of the pressing and drawing occurs in the higher part of fingers are at liberty to play. Be very careful not to draw the right-hand board, where the two draw-notes, LAH and TE, or press the bellows without either opening the valve or press are required to follow each other. Our diagram will explain ing one of the pegs. If you use such careless violence, the this. The first and second pegs of the left-hand board give metallic tongues would soon be put out of tune. The use of the notes which are very useful as accompanying harmony, but of valve is this : if you have drawn out the bellows to the full harmony we must not begin to speak at present. With this extent, and wish for the production of some note, to draw them instrument our pupils can play most of our exercises. They can again, hold down the valve and press the bellows. The air will play them in two parts if they please. Two of the "accithas escape without a sound, and you are at liberty to draw the dentals,” those most frequently occurring, can be obtained on bellows again just as you please. If you have pressed down the instrument with two rows of pegs. Thus, if you are the bellows to the full extent, and should wish to press them playing in the key of c—that is, on the higher row of pegsyet again, you can, in a similar way, draw with the valve held you can get the “accidental,” which we call FE (commonly down, and then press as you please. Holding down any one called the sharp fourth, but really the seventh of a new key, of the pegs with your finger you can produce two notes, one of which we shall have more to say in future lessons), by drawing while the bellows is pressed together, and the other while it is on the first peg of the lower row on the right-hand board, or on drawn out. We have affixed to the pegs in the diagram the the second peg of the left-hand board. FE is, in fact, the Te of sol-fa names of the notes which they produce. Those printed in another key. Again, if you are playing in the key of G—that is, capitals are produced by pressing the bellows, those in small on the lower row of pegs-you can get the “accidental” TA letters are produced by drawing out the bellows. These sol-fa (commonly called the flat seventh, but really the fourth of a names of the notes apply to both rows of pegs alike; the higher new key), by drawing on either the fourth peg of the left-hand row of pegs playing in the key of c, and the lower row in the key board or the third peg of the right hand board. TA is, in facty of G.
the Fah of another key. The learner will notice that all the press-notes are those of the Of the other difficulty of our correspondents, the “ movable tonic chord DOH, ME, SOh. So that if you were to hold down DOH, or key-note,” we must speak in the next lesson. Meanall the pegs at once, and press the bellows, you would produce time let our pupils practise carefully the following exercise. good harmony. This is a great help to the memory. Let the It is intended to exhibit the contrasted effects of me and sou papil who possesses such an instrument begin by holding down (the third and fifth of the scale) in a somewhat quick move. the middle peg of the left-hand board, and pressing the bellows: 1 ment.