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I used the common syringe, and filled the leg with the liquid. We then placed it in cold water, and allowed it to remain until the next morning.

The first work was to remove a piece of the skin, and take sections of it by the aid of a Valentin's knife. The arteries were shown beautifully; but the most attractive part was where the growth of the hair was laid open before us. Each hair exactly resembled a common onion, whilst every bulb was surrounded by a perfect network of arteries; and where any bulb had been torn out by accident, there was left a minute bird's-nest of them, clearly showing how they had been intertwined around some lost friend. Different sections of the muscular portions showed every phase of arterial distribution, with some exquisitely minute vessels in parts. I then took an artery and cut cross sections, in which the carmine portions were as closely interwoven as wickerwork. I also, with a pair of scissors, laid open a length of the artery, and mounted it, together with a cross section. In the same way I used the veins. Many of the nerves we took out, and, after cleaning carefully with knives and small brushes where necessary, mounted them with the attendant arteries around them. But as we approached the hoof, double interest was given us. The skin with its hairs just above the hoof plainly showed the change taking place, and sections of the hoof gave beautiful specimens of where circulation was gradually stayed by the growth of harder substance. Here, too, we reached the laminæ, or thin plates (somewhat resembling the gills of certain fishes), the exact use of which, we have no space to discuss-and these were readily removed by the aid of scissors and knife. In these the vessels are minutely and exquisitely shown.

These are a few of the beauties which this injection afforded me. My friend Mr. Hepworth and I worked together at this subject for a week or two, and part of the knowledge which he gained from it was communicated to

the microscopic world in the fifth volume of their Journal, where the illustrations are beautifully printed. We took about 1,000 slides from this leg, but could easily have taken a specimen for every microscopist in the country. What few slides I now have are mostly mounted in balsam, and are quite as good in colour and every way as beautiful as on the day they were mounted.

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CHAPTER VIII.

MISCELLANEOUS.

Ir must be evident to all readers that there are various objects of interest to the microscopist which cannot be properly placed amongst any of the forementioned classes, but must not be omitted in such a guide as this professes to be. Of these may be mentioned the circulation of the blood in various animals, the rotary motion of the fluid in many plants, the best means of taking minute photographs, &c. &c.

Perhaps the most interesting of these objects is the cireulation of the blood through the finer vessels of various parts of animals used for these purposes, which parts, it is evident, must be very transparent to afford a perfect view of this phenomenon. The web of the frog's foot is very frequently employed, but requires a certain arrangement, which we will now describe. A piece of thin wood (Dr. Carpenter recommends cork) is taken, about eight inches long and three wide; about an inch from one end is cut a hole, half or three-quarters of an inch in diameter. The body of the frog is then placed in a wet bag, or wrapped in wet calico, whilst the hind foot projects; the whole is then laid upon the piece of wood, so that the foot, which is left free, may be extended over the hole. The web must then be spread out, and secured, either by loops of thread fastened to the toes and attached to small pins placed around the hole in the wood, or the pins may be inserted into the wood-through the web. A few bands of tape must be passed round the body, the leg, and the wood, to prevent any disarrangement arising from the struggles of the animal. Care must be

taken that the tape be not too tight, else the circulation will be very slow or altogether stopped. The wood must now be fixed upon the stage, with the aperture under the objectglass: this is sometimes done by simply binding it, or a spring is fixed so as to accomplish the same object without so much trouble. With a half-inch power the blood may be seen to flow very distinctly. The frog may be used for hours if care be taken to prevent the web from becoming dry, by wetting it with a little water from time to time. The piece of wood or cork upon which the frog is laid is often made to give place to the "frog-plates," supplied by opticians. These are made of brass, somewhat resembling the piece of wood above recommended, but each maker's pattern differs, according to his own taste.

The tongue of the frog is also sometimes used for the purpose of showing the circulation of the blood, which is done in the following manner :-The body is wrapped with calico, and made fast to the plate as before, only the mouth of the frog is brought to the opening. The tongue is then gently drawn out of the mouth and pinned down over the aperture, when the circulation will be well shown. But, as Dr. Carpenter observes, the cruelty of this mode of treatment is so repulsive that it is unjustifiable.

Tadpoles of the frog (which, of course, are only obtainable in their season) are good subjects for showing the circulation of the blood. They are best suited for the microscope when about one inch long. The tadpoles of the newt and toad also are equally suitable. They may be placed in a very shallow glass trough with a little water, and a narrow band of linen bound lightly round in some part not required for examination, to keep them from moving; or they may be laid upon a glass plate with a drop or two of water, and a thin glass covering lightly bound upon it. Dr. Carpenter, however, places them first in cold water, gradually adding warm until the whole becomes about 100°, when the tadpole becomes rigid, whilst the circulation is still maintained. I have not, however, found this necessary, the thin glass ac

complishing all that is desired. The tail is generally the most transparent, and shows the circulation best; but in some of the newt larvæ the blood may be traced down to the very extremities if they are not too old. Mr. Whitney places the tadpole upon its back, by which means the heart and other internal arrangements may be seen.

Amongst fishes also may be found subjects for the same purpose, but they seldom furnish such good examples as those before mentioned, because the blood-vessels are not nearly so abundant as in the foot of the frog, &c. The stickleback is, however, procurable almost in any place. during the summer months, and may be laid in a shallow trough, loosely bound down as the tadpole. The tail may be covered with a piece of thin glass to prevent him curling it to the object-glass. The power needed for this will be about the same as with the other subjects; viz., a half to a quarter-inch object-glass.

It is not absolutely necessary to go to reptiles or fishes for this curious sight, as some other animals serve very

well.

In the wings of the common bat may be found a good subject. These must be stretched out on something resembling the frog-plate before described, when those parts near to the bones will show the largest vessels very clearly. The ear of a young mouse is an illustration of the same phenomenon, but it is very difficult to fix it in a good position, as these animals are so very timid and restless.

Amongst insects also the circulation may be seen by placing them in the cage, or live-box, so as to keep them still, but not to injure them by too much pressure. In certain larvæ it is particularly well shown, as in those of the day-fly and plumed gnat; but in some of these the blood is almost colourless. In the wings also of many insects this circulation is well seen, as in those of the common housefly; but as these parts become dry in a few days, the subject should not be more than twenty-four hours old.

Somewhat approximating to the forementioned phenomenon, is the rotation (or cyclosis) of fluid in the cells, or,

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