"muscular membrane" envelops the whole body, in common with the skin, and attached to it are transverse muscles which constitute the boundaries, as it were, of the rings of the body. These muscles, by their contraction, impart to the little Tubifex its undulating and longitudinal movements, and a probable modification of them is found in another set of muscles at the mouth of the animal, these latter being intended to regulate the movements of the pharynx (fig. 1 e).

The reader will no doubt be somewhat surprised to hear that so diminutive an organism should be furnished with a complicated nervous system, perfectly adapted to its general structure, and for the fulfilment of its wants.

A careful examination of the little annelide is necessary for the definition of the nervous system, which is found to resemble the other forms of this order. It consists of a long double cord of nervous fibre, which runs throughout the length of the worm, and gives off in each segment of the body three pairs of nerves, which direct the movements of the muscles belonging to that ring. The points in the nervous cord whence these nerves spring are slightly enlarged, and are called "ganglia" (fig. 3).

In the first ring of Tubifex we find a very large ganglion (fig. 3,a), the two nervous cords enlarging into a round mass composed of nervous matter; this represents the brain of higher animals, and from it spring two pairs of nerves, one of which is connected with an organ supposed to be the eye; but of this there is great doubt. We ourselves have tried several experiments to ascertain whether the Tubifex has been favoured with organs of sight or not, and have come to the conclusion that it is blind. The Creator has nowhere exercised his Almighty power uselessly, and eyes would certainly be of no use to our little annelide, as his food consists merely of the mud which he inhabits, from which all the nutritive matter is extracted in his intestinal canal.

Strange though it may seem, the Tubifex is provided with a liver, and a very large one too, and is therefore liable, in common with the human race, to bilious attacks. The intestine is covered throughout its length with a dark yellow membrane containing curious little granules (fig. 14), and capable of secreting and projecting a fluid into the intestine-this is the liverand is no doubt most important in digesting such bonnes-bouches as Thames mud affords.

The animalcule is also provided with excretory organs answering to the kidneys in higher animals-there are two in each ring of the body-consisting of little tubes with an internal and external opening covered internally with minute vibratile hairs or "cilia," which are also continued around the expanded orifices, as seen in fig. 6. When the Tubifex is placed under the microscope, these "cilia" may be seen in rapid motion,

and present a most beautiful appearance. The same excretory tubes may be found in the common earthworm (Lumbricus terrestris), and are there visible to the naked eye. These cilia are found in other parts of the body-the interior of the intestine is lined with them, and they are easily seen at the extremities of the body, in continuous movement when the Tubifex is under the microscope.

We must now say a little more about the blood-vessels of our worm Besides the long vessel which runs along the intestine, called the dorsal vessel, we find another placed below the intestine, of rather smaller proportions, also running through the whole length of the body. These two blood-vessels are connected by smaller ones, as seen in figs. 1 and 2-a pair in each ring of the body; in the seventh ring of the body, counting downwards from the cephalic or head-segment, we find the two hearts, which are merely enlarged lateral vessels (fig. 2 a and fig. 1 d). It is a most beautiful sight to see these little hearts contracting and expanding while they send the blood through the various ramifications of the blood-vessels. In the region of the reproductive organs (from the eighth to the sixteenth ring of the body), there is an interesting modification of the lateral vessels. They are connected by two vessels which run parallel with the great dorsal and ventral arteries, the arrangement of which will be best seen from the plan of the circulation given in our drawing (fig. 2).

We must now say a word or two concerning the reproductive apparatus, which is very complicated, the male and female organs being, as we before said, united in the same individual. In the eighth ring of the body, underneath the intestine, there is a round semi-opaque mass (fig. 5 a); this is the male glandular organ, and at the proper season of the year it is full of the spermatic filaments, which are often found collected together in discs somewhat resembling the beautiful little Sun animalcule (fig. 8). At a certain period the case enclosing these " Spermatozoa" bursts, and they float into the cavity of the body; thence they pass into a pair of ciliated tubes which are found coiled up in the tenth ring of the body (fig. 4 d and fig. 5 e). These little tubes, like the excretory tubes, have large trumpetshaped mouths, and are lined with minute cilia, the arrangement of which is seen in fig. 11. The arrangement of the other organs of reproduction will be best seen in figs. 4 and 5. The ovaries (fig. 4a), contain eggs in all stages of development, which pass from them into a large cavity where they are probably fecundated, as we find the ciliary tubes likewise connected with this part of the body. At the time that the eggs are deposited they are enveloped in little gelatinous capsules, each containing two or three eggs (fig. 10). These little capsules

are formed by two glands found in the eighth ring of the body (figs. 7 and 5 b); they present a most beautiful structure, being composed apparently of polygonal cells: in their interior are found little vermiform bodies which assist in the secretion of the fluid that forms the egg-capsules. The eggs are probably deposited by a spontaneous dehiscence or rupture of the body, there being no natural outlet. Fig. 9 represents a (probably) secretory organ met with in the ninth ring of the body. Its function is not known.

Whilst speaking of the circulatory system we should have mentioned that the general cavity of the body is filled with a fluid which surrounds all the internal organs. It contains numerous small granules of various sizes, very similar in appearance to those found in the quasi liver enveloping the intestine (fig. 15). This liquid is probably merely pure water which brings the needful oxygen to the capillaries of the Tubifex, and answers the purposes of respiration. Such an arrangement is met with in many annelides, and is known as the chylaqueous system.

Our little Tubifex not only presents us with a wide field for study and amusement in the investigation of its anatomy, but it actually forms the habitat of at least two very interesting forms of animal life. One of these is met with in the interior, the other attached to the exterior of the body. The animalcule which resides in the interior of the Tubifex is a species of Opalina; it is very minute, and is covered by spiral rows of cilia, giving it, when in motion, an extremly beautiful appearance. It is one of the lowest forms of animal life belonging to Ehrenberg's class Infusoria. The other parasite which we have met with in studying the Tubifex is the beautiful Vorticella. We have examined but few specimens without finding a cluster of these exquisite living forms attached to the head or tail of the worm. The Vorticella, like the Opalina, is very low in the scale of creation, but it is of an entirely different form: supported by contractile stems there are numerous cup or bellshaped bodies fringed round their margins with beautiful cilia. Thus it will be seen that even in localities and substances which are repulsive to the ordinary mind, the inquiring student may find living forms of intricate structure performing complicated natural functions, and affording a habitat for still simpler but equally interesting forms of life. Even this imperfect and cursory review of the anatomy of the little Tubifex cannot fail to have afforded confirmation of the great truth, that all things are created in wisdom, and we may once more repeat that not only is it possible for the thoughtful man to read sermons in stones," and find "books in running brooks," but that even the muddy bed of a broad river yields its volumes for the edification of the inquiring mind.

ANESTHETICS.

BY T. L. PHIPSON, M.B., PH.D., F.C.S.

BY

Y anaesthetics are understood certain substances which have the property of inducing a peculiar state of the nervous system called anesthesia, and thereby rendering us insensible to pain. They rank among the most powerful, and, at the same time, most useful agents that man has hitherto obtained from the hidden treasures of nature. From the moment of his birth (and perhaps even some time before birth), man is liable to experience what is called pain. The human body is so organized that, in a state of perfect health, we feel nothing; and there are some persons, though few indeed, who pass through life almost without knowing what pain is, whilst others again are almost constantly in a state of suffering. When pain is felt in any part of the body, that part is not in its normal condition, it is no longer in the state of insensibility which characterizes perfect health.

But pain is not without its uses: it warns us from danger, and without its existence our own existence would infallibly cease. For instance, if no pain were felt when the hand or foot is placed in the fire, we should not be tempted to withdraw it unless we happened to see it consuming. Some time ago a labourer lost his leg by sleeping too near a lime-kiln; he felt nothing till he awoke, when it was too late. Likewise, if no pain were felt when boiling water, or some powerfully acrid substance, is poured down the throat, we should not be tempted to desist from introducing it into the body, and so our life would, sooner or later, be inevitably destroyed. In lower animals, where the organs of sensation cannot be detected so distinctly as in man, and in some where such organs seem indeed to be completely wanting, there is still an existing faculty equivalent to pain, and followed by similar effects: thus, if we touch the tentacles of a sea-anemone, in which organs we can find no nerve-fibres, the animal instantly withdraws them as if hurt, in the same manner as a dog would withdraw his leg if his foot were pricked with a pin. In the human body, we have three kinds of nerves: viz., the nerves of sensation, the nerves of motion, and the nerves of organic life, which govern the functions of digestion, respiration, secre

tion, &c. But these three kinds are so intimately connected in the animal economy that one of them may, in certain cases, react upon the others, so that all three are capable of giving rise to pain; the first directly, and the others indirectly, by acting through the first. But happily for us, the study of nature has placed in our possession several means of allaying pain; it has procured us a series of substances which act upon the nervous system so as to deprive it of its faculty of producing pain, sometimes partially, and sometimes most completely, without interfering in any great degree with the other functions of the body.

Some of these means of allaying pain consist in producing sleep, either perfect or partial. The physiology of sleep is little understood, and, indeed, next to life and death, sleep is perhaps the most inexplicable phenomenon inherent to our nature. At certain intervals, we feel an irresistible desire to repose, and sleep comes on gradually. Its influence is felt by certain portions of the nervous system; other portions never sleep. The nerves of organic life continue their functions during sleep, the heart beats, circulation goes on, respiration and digestion continue, but the nerves of motion and of sensation have momentarily lost their power; consciousness is gone, voluntary motion disappears, hunger and thirst are absent, and so likewise is pain. Such is complete or perfect sleep. But it happens sometimes that sleep is partial or imperfect, and then some curious phenomena are observed. Intelligence may be more or less active, and sensation may be possible to a greater or less degree, but never to so great an extent as in the waking state. Generally, in imperfect sleep, consciousness is only partial, volition incomplete, and sensation dull. This state of incomplete sleep gives rise to dreams and to somnambulism. The former are odd manifestations of the intelligence no longer completely conscious. The latter may be either natural or artificial (mesmerism).

In somnambulism the intelligence is more active than in an ordinary dream; the nervous system, only partially subdued by sleep, is capable of bringing into action the senses and motion, but the faculty of feeling pain is almost, if not entirely absent, and moreover the somnambulist has no consciousness of danger. Hence natural somnambulism, which varies in intensity from simple sleep-talking to the most remarkable physical and intellectual feats, is a dangerous condition, inasmuch as we are no longer able to take care of ourselves. However, somnambulists have frequently avoided dangers in the most astonishing

manner.

Artificial somnambulism, or mesmerism, as it is sometimes