green. The section is stained in a small dish containing alcohol, to which a few drops of eosin have been added. Time various; from half an hour to several hours; being left too long in the eosin is not detrimental. The section is then rinsed in water, whereby it loses some of the eosin, and is then laid in a watch-glass filled with a solution of one of the other colours, and allowed to remain some minutes till it is coloured very deeply, almost black. After the section has been again rinsed in water, it is placed in alcohol, which possesses the property in a very high degree of dissolving both the colours. This is the most critical part of the process, i. e. hitting the right moment when both the colours have been just sufficiently drawn out. It is a good plan to take the section out, and view it in oil of cloves under the microscope, and if found too deep, to replace it in the alcohol. In general it is better to remove the preparation when still too blue, as the eosin is drawn out somewhat quicker than the other colours. The oil of cloves, in which the preparation is put after the alcohol, does not affect the eosin, whilst it dissolves (in a somewhat different degree of intensity) the other colours. Any desired relation between the colours can thus be obtained. When the proper tint is reached, the oil of cloves is sucked out as completely as possible by blotting-paper (the best plan is to lay the paper on one side of the preparation on the stage, and place the stage slanting), then apply Canada balsam dissolved in chloroform for a covering. In this no further change takes place. If too much oil of cloves is left behind, a further extraction of the blue takes place, and the object is surrounded by a blue halo. This should therefore be carefully avoided.

As to the distribution of the colours over the different parts of the tissues, the blue (or the green) pigment stains principally the nuclei of the cells, and the eosin the cell-bodies, and attention may be drawn to the various shades of colour which appear in these latter, produced by the mixture of the red with the blue pigments, conditioned apparently by the mixture of the other cell-contents with the protoplasm, or by the changes produced in the protoplasm by age. With regard to the secretions of the cells, as far as these from their soft or firm consistency allow of being distinguished in microscopic sections, the former are generally stained more blue, the latter more red, often simply eosin red. Thus the contents of the goblet cells, whilst still contained in the cells or out of them, appear a deep blue, the interstitial substance of the hyaline cartilage light bluish, the cell-membrane eosin red, the elastic fibres brilliant red, the connective-tissue fibrillæ dark rose, the bone deep scarlet; a very peculiar and entirely characteristic colour is shown by the red blood-corpuscles, which are bright scarlet. In the blood of the lower vertebrate animals, which have nuclei in their blood-corpuscles, this colour forms a still greater contrast to the deep blue nucleus. The staining is so intense that sections of organs whose blood-vessels are still coloured with blood-corpuscles look as if injected, so strong is the contrast between the scarlet and the other tints.

*Alcoholic solutions of these do not stain enough to be of use, therefore the eosin cannot be mixed with the other colours.

With regard to the particular organs, I have to remark as follows:(1) The Skin.-This is one of the objects which gives the best results. The different layers of the epidermis, and the whole epidermis contrasted with the cutis, show very prominently. In the cutis the dark, rose-coloured bundles of fibrilla of the connective tissue appear remarkably distinct, so that their arrangement is easily recognized. Upon this rose-coloured substratum are seen with extraordinary distinctness the blue nuclei of the connective-tissue cells, the vessels with their scarlet contents and their musculature, and the sweat glands with their somewhat dark-blue stained cells, on the borders of which may be detected, on the exuding side, the fine red cuticula. Hairs and nails are also very beautiful.

(2) The Muscular System.-This is not very well adapted for the staining, as regards details. On the other hand, the tissue, as such, stands out very beautifully from other tissues. The smooth muscles, for instance, are distinguished in weak stainings from the surrounding connective tissue; they remain dark red, with a different tint to the connective-tissue bundles. The striated muscles have a somewhat darker tint.

(3) Bones and Cartilage. The basic substance of the decalcified bones becomes deep scarlet, the cells more bluish. The method is best suited for the process of ossification. In this appears the peculiar phenomenon, that in the place where the cartilage cell nests lie the interstitial substance of the cartilage, which previously had a bluish red tint, acquires somewhat suddenly a deep blue colour, which would be the characteristic colour of the calcified cartilage. The basic substance of the bone, as above mentioned, appears stained a deep scarlet, and thus the superposed bone substance proper, down into the bone, is distinguished very clearly from the calcified cartilage. On the other hand, by this means the latter may be followed far into the bone, as every trace of it may be recognized, without anything else, by its blue staining. Thus it is possible to detect the cartilageremains very plainly in the middle of the shaft of the bone, in a transverse section through the tibia of a new-born infant. The hyaline cartilage, with its bluish basic substance, and the red cells inserted in it, with a number of blue nuclei, is a most excellent object. The perichondrium is a deep red, and thus contrasts sharply with the cartilage. The division of the basic substance of the cartilage into different territories often appears very beautifully; the bounding parts are almost blue black. Elastic cartilage gives most excellent preparations; for instance, the transition portion from hyaline to elastic cartilage (e. g. cartilago arytenoidea). The elastic fibres are a lively red, and are thus well distinguished from the bright blue basic substance.

(4) Nerve System.-Transverse sections through the spinal cord show the coarser fibres very well, as the nerve-tubes, both medulla and axis-cylinder, are coloured red, whilst the neuroglia appears bluish red, with dark blue nuclei. The ganglion-cells are reddish, with a slight touch of blue, whilst their nuclei, in opposition to the nuclei of the other cells, appear somewhat redder than the cell

substance. The nucleolus is generally a deep dark red. The double staining is specially recommended for the cerebellum, to make the granulated layers conspicuous. The Purkinje cells remain quite red, both nucleus as well as cell. I cannot recommend it, however, for the peripheral nerve system. In some few special cases it is applicable. The nerves in the bladder of the frog are very finely displayed. Methyl-violet (not the other colours) stains the fine nerves in the skin of the lamprey very beautifully.

(5) The Alimentary Canal.-We now come to a region in which the method answers very well-the glands; for, first, we are able to find constant differences in the staining of different glands; and secondly, in many cases, differences in the staining of the cells of the same glands, according to their condition. A very fine example of the first case is furnished by the aquiparous and muciparous glands in the root of the tongue. The first show a bright red protoplasm, with beautiful blue nuclei; the muciparous are stained with such an intense blue that the nucleus is often not visible. Both kinds of glands stand out also splendidly from the red muscular substratum. Examples of the second case are the gl. submaxill. and sublingualis. In the socalled state of rest, the cells are coloured uniformly blue, although not with the same intensity as the muciparous glands on the body of the tongue; the still darker blue nuclei lie, as is known, as though pressed flat close to one edge. In the so-called state of activity the cells are a granulated red colour, with round blue nuclei in the middle. The half-moons' are always red. The parotid has bright red cells, with blue nuclei. The pancreas is similar, only that the tint is rather bluer. One gland, the lachrymal-which, however, does not belong here has most peculiar red cells.

The epithelium of the mouth, tongue, and oesophagus separate themselves, on being stained, into a superior and inferior layer, and the epithelium and the glands of the stomach and intestines are excellently adapted for the staining."

The effects of the staining on (6) Liver, (7) Organs of respiration, (8) Urinary organs, (9 and 10) Male and female sexual organs, (11) Blood-vessels, (12) Lymphatic glands, &c., and (13) Organs of sense, are detailed in a similar manner, but must be omitted here for want of space.

The Ordinary Microscope as a Polariscope for Convergent Light.In reference to Professor A. de Lesaulx's suggestions on this subject (see p. 207), M. Bertrand claims to be an independent discoverer with the Professor of the advantages to be derived from adding two achromatic lenses of short focus above the lower Nicol. He places, however, a third achromatic lens of about 3 centim. focus above the posterior lens of the objective, at a distance a little greater than the focus, and capable of being slightly moved nearer or farther from the objective according to the power used. It should also be able to be removed easily from the microscope, so as to allow of the object being viewed in the first instance by parallel light.

New Aerobic Vibrion.-M. H. Toussaint has recently described a vibrion which he found in a rabbit inoculated with the blood of a

horse which had died rapidly of malignant pustular fever. The blood was received sixty hours after the death of the horse, and its state of preservation was such as to enable the author to affirm that it had never contained bacteria. A rabbit was at once inoculated by two punctures in the ears, which died in twenty-four hours afterwards, no bacteria being anywhere found. A second rabbit was then inoculated, which died in thirteen to fourteen hours, and it was in the latter that the new vibrion was discovered. Fifty-four other animals were subsequently inoculated, with the same results. When the blood was examined under the microscope with a power of 500 to 800 diameters, a great number of extremely small vibrions were seen, spherical or slightly oval, of very little refracting power (which makes it difficult to distinguish them in the coloured serum), single or in pairs, never three in a chain. Their dimensions vary little, being 0004 mm. in thickness, and 0005 mm. to 001 mm. long, the latter dimension attained only by vibrions which have just separated. Their only movements are feeble and slow, which clearly distinguishes them from Brownian movements. Whilst very numerous in the blood (five to ten to a globule), they exist in immense quantities in the lymphatic ganglions, and swarm in the cedema at the point inoculated. They are found in all the tissues outside the vessels, and in all the fluids-the humours of the eye, the serous fluids, and the urine. When the epiploon is examined with a strong power, they are clearly distinguished in the interior of the vessels in the form of a mass of regular granulations which often occupy the whole breadth of the capillaries, and stand out in relief at their optic margin.

All the fluids can be inoculated in the same way as the bloodinoculation of the aqueous humour, the urine, and the chyme kills the animals in twelve hours. The disease is not only contagious by direct inoculation, it is equally so by the alimentary canal, and perhaps also by the respiratory passages. Three rabbits died in eighteen to twenty-four hours after having eaten oats soaked in the infected blood. Excrement powdered and mixed with the food killed two rabbits out of six who had such food on one occasion. Two other vigorous rabbits died the next day, after having passed one night with two inoculated ones, and three adult rabbits in adjoining boxes died in the same way without any direct contact.

M. Toussaint cultivated the vibrions by M. Pasteur's method, and under the microscope in the gas and warm chamber of M. Ranvier, and was able to establish that in two hours and a half a single one had produced twenty-two. The multiplication took place by scission as soon as the vibrion had doubled in breadth. Filaments analogous to those of the bacteria were never formed. They multiplied more rapidly at the sides next to the air-groove than in the middle of the preparation.

Contact with air or pure oxygen in a moist chamber for twentyfour hours preserved a layer of blood of mm. in thickness in full activity. In tubes free of air and sealed, the blood lost its activity at the end of ten days. Putrefaction destroys the vibrion, but much more slowly than the bacteria.

When mixed in the culture liquids the bacteria and the new vibrions develop side by side. When animals are inoculated with them (taking care to have only a very small quantity of the latter) the two parasites are developed simultaneously, and on a microscopic examination are found associated in the blood. But on the second inoculation the bacteria are still localized at the point of inoculation, whilst death has already taken place in consequence of the much more active multiplication of the vibrions.

In a foot-note the author adds that he has found Ranvier's warm chamber extremely convenient for studying all the lower beings, and particularly bacteria. Their elongation can be followed minute by minute, and the transformation into spores as well as the elongation of the spores to re-form the bacteria. He was thus able recently to determine that the bacteria cultivated in certain liquids, especially in the serum of the blood of the dog, give sometimes true sporangia, globular or in "calabashes" filled with spores."

"The Projection of Microscope Photographs."-Dr. J. C. Draper, Professor of Natural History in the College of the City of New York, contributes an article under this heading to the American Journal of Science and Arts.' In the lanterns that are constructed for the projection of photographic or other images on a screen, the support or stage on which the photographic slide is placed is close to and at an invariable distance from the condensing lens. So long as the objects to be projected are nearly equal in size to the diameter of the condenser, this is the only adjustment that can be made to illuminate the whole surface of the object, but when the diameter of the field occupied by the object is only one-half or one-quarter of the diameter of the condensing lens, the brilliancy of the result obtained upon the screen may be greatly increased by removing the supporting stage or object carrier to a greater distance from the condenser, so that a convergent beam of light may fall on the object to be projected. To accomplish this I have constructed the following form of lantern.

In the figure, a is a zirconia light mounted on an adjustable base,† which may be used with a condensing lens of very short focus, since the zirconia is not burrowed into cavities where the oxyhydrogen flame impinges, as happens with lime cylinders, and causes the flame to be reflected on the condensing lens, and thereby destroys it. In the jet employed, the gases are mixed just before they are ignited. b, b is a short-focus condensing lens; c, the stage or support carrying the photographic or other design to be projected; d, the projection lens formed of three sets of lenses, and giving a perfectly flat rectilinear field; a, c, d are mounted on a base board e, f, to the end of which the lantern box a, b is attached, and which is freely opened above and below to permit perfect ventilation. The base carries lateral grooves in which a, c, d slide, allowing them to be placed at varying distances from b, and fixed by suitable binding screws; c and d are also connected together by a rod r, carrying an adjustment screw at r, by

* Comptes Rendus,' vol. lxxxvii. p. 69.

+ See American Journal of Science and Arts,' Sept. 1877, p. 208.