ous tissues (Journal of the Royal Microscopical Society, July, 1878).

Rapid Staining by means of Carmine.

Dr. H. Obensteiner states that sections of the nerve system (brain and spinal marrow of man and animals) may be rapidly stained by placing the sections in a watch-glass containing the carmine solution, and suspending them in the steam of boiling water; from two to five minutes are required. After the staining is completed the sections are washed twice in distilled water, placed for a few minutes in common alcohol, and for the same time in absolute alcohol, and, finally, in oil of cloves for examination. The preparations thus treated are colored in a specially sharp and distinct manner-e. g., the connective-tissue corpuscles, together with their long continuations into the substance of the brain, which insert themselves into the adventitia of the vessels, come out with a distinctness which it is difficult to obtain by other means (Archiv für Mikroskopische Anatomie, vol. xv., 1).

Gold Staining, and the Termination of the Nerve in the Unstriated Muscles.

Professor Ranvier recommends the following modification of the gold method in a recent communication to the French Academy. The preparation is placed for five minutes in fresh lemon-juice, filtered; then it is put, for fifteen or twenty minutes, in three cubic centimeters of a 1 per cent. solution of chloride of gold; then in twenty-five to thirty grams of distilled water, to which is added one or two drops of acetic acid. Two or three days afterwards, when under the influence of sunlight and the slightly acid medium the reduction of the gold has been effected, the preparations are ready for examination. Fragments of striated muscles, treated as above, or, better, when, after having been subjected to the action of the gold, they have been placed for twelve hours, sheltered from the light, in a 20 per cent. solution of formic acid, and then prepared by teasing, show the terminal nervous arborizations admirably clear, and colored a deep violet. The author finds: (1) In the unstriated muscles, the nerves terminate, as in the striated muscles, at the surface of the muscular elements by an expansion, more or less ar

borized, of the cylinder-axis. (2) The nervous net-work of the involuntary unstriated muscles is in connection, not with the elementary nervous action which sets the muscle in activity, but a more complex action, on which depends the functional energy of an organ whose activity is derived from the direct action of the nervous centres.

MISCELLANEOUS.

New Acarus.

A new acarus, Cheyletus flabellifer, is described by A. D. Michael, F.R.M.S., which he found feeding upon the rare acarid Glyciphagus palmifer. But one species of Cheyletus was before known, and from it the present form differs in being more thick-set and powerful, and the hairs, instead of being fine, are developed into fan-shaped expansions. The color is yellowish-white (Journal of the Royal Microscopical Society, July, 1878).

Insect Dissection.

Mr. W. T. Loy uses the following simple apparatus for insect dissection. An upright iron rod is fixed into a heavy metal foot; round this rod is coiled one end of a stout wire, the other end being bent into a ring to hold a watchmaker's eye-glass. This arrangement, by pressing the head down, focuses the lens upon the work, while both hands are at liberty. With this simple apparatus Mr. Loy has made some very beautiful dissections. A very good condenser may be made out of a Florence oil-flask, cleansed and filled with water, and then securely corked. The medium most suitable for dissecting in is glycerin (Jour. Quek. Mic. Club, Jan., 1878).

Pedesis.

Professor Stanly Jevons, in objecting to the names "Molecular movement," "Brownian movement," and "Dujardins titubation," for the movement of particles suspended in liquids, suggests pedesis from the Greek-leaping, or bounding. The best exhibition of this motion is to be got by grinding up a particle of pumice-stone in an agate mortar, and mixing it with distilled water. The minute particles will be seen under the microscope to leap about with an in

cessant quivering motion, so rapid that it will be impossible to follow the course of a particle. The most convenient substance is kaolin, which, when shaken up with pure water to make a milky liquid, shows the motion in great perfection. This motion, he states, is not due, as has been suggested, to rays of light or heat; nor is it connected with the shape of the particles; nor yet is it due, as Tyndall has supposed, to surface-tension. Pure water exhibits pedesis in the highest perfection, even the air, and carbonic acid usually dissolved in it, producing a perceptible difference; by the slighest addition of sulphuric acid the movement is almost entirely destroyed, and, as a general rule, by all salts and soluble substances. The exceptions are, pure caustic ammonia (but not its compounds), boracic acid, and silicate of soda-gum arabic even possessing the power of increasing the motions. The Professor draws a parallel between Faraday's experiments in the production of electricity by the Armstrong electrical boiler and his own in pedesis, and finds that those substances which prevent or modify the production of electricity operate in the same manner in preventing or modifying pedesis; and hence he considers it as an electrical phenomenon. In attempting to explain the exact modus operandi, we can only speculate that the action upon minute irregular fragments will never be exactly equal all round. In order that a particle shall rest motionless in a non-conducting fluid or poorly conducting one, as pure water is, it must be in exact equal and chemical electric relation to the fluid on all sides. It is almost infinitely improbable that this should happen, and a condition of unstable equilibrium within limits is the result. The Professor concludes by pointing out that there is probably a close connection between pedesis and the phenomena of osmose (London Quarterly Journal of Science, April, 1878).

Since the publication of the preceding investigations, Professor Jevons, in making some experiments with a view of testing the opinion of Professor Barrett and some other physicists, that pedesis was due to surface-tension, and who have suggested soap as a critical substance, inasmuch as it reduces the tension of water, in which it is dissolved, without much affecting (as is said) its electric conductibility, found that, with a solution of common soap, the pedetic mo

tion was considerably more marked than before, and he bases on this his explanation of the detergent power of soap. It seemed unaccountable that for cleansing purposes the comparatively neutral soap should be better than the alkaline carbonate itself. The fact is, the detergent action of soap is due to pedesis, by which minute particles are loosened and diffused through the water, so as to be readily carried off. Pure rain or distilled water has a high cleansing power, because it produces pedesis in a high degree. The hardness of impure water arises from the vast decrease of pedesis, due to the salts in solution; hence the inferior cleansing power of such water. By the addition of alkaline salts and soap, we have the alkali dissolving and the pedetic cleansing power. At the same time we have a clear explanation why silicate of soda is now largely used in making soap, this being one of the few universal substances which increase the pedetic and suspensive power of water.

New Journals.

Two new journals devoted to microscopical science and kindred subjects have been commenced during the past year-Brebissonia, published in France, and the American Quarterly Journal of Microscopy, published in New York. The former is a spicy little journal, published monthly, and devoted principally to Algology and Microscopical Botany. The latter is more extensive in its aims, and promises to be an honor to American journalism.

National Microscopical Congress.

A so-called National Microscopical Congress was held at Indianapolis, August 14-17, 1878, to which most of the leading microscopists of the United States were invited, and in which many of them participated. Some sixteen microscopical societies were represented by delegates, and many creditable papers were read. Of course, in this first meeting there was much informality, and some resolutions were introduced, and some adopted, which, no doubt, will be reconsidered at the next Congress, which is to be held at Buffalo, N. Y., and will be much better attended.

The Limit of Accuracy of Measurement with the Microscope. Professor W. A. Rogers, of Cambridge, presented a paper at the meeting of the National Microscopical Congress at Indianapolis, on the Limit of Accuracy of Measurement with. the Microscope. He finds that two experienced observers can measure the distance between two lines, and obtain figures agreeing within such narrow limits that they are almost identical. The following conclusions are drawn by Professor Rogers: 1. Two equally skilful observers can measure the same space within about gooʊ of an inch, if the space does not exceed of an inch; for a space of T of an inch, the deviation will probably amount to go of an inch, in case the measurements are made with a filar micrometer. 2. The average deviation for accumulated errors, under similar conditions, is not far from ʊʊ of an inch for eleven intervals. For a large number of intervals the deviation will be somewhat larger, but it will not be proportioned to the number of intervals.

Microscopic Tracings of Lissajous Curves.

Mr. R. G. West has been successful in tracing these curves on glass, in lines 55,000 to the inch, and in some respects they are considered better fitted for microscopical tests than parallel rulings. Aside from their great beauty, and the necessity for skilful illumination to display them well, the intersection of some lines and the gradual approximation of others, arising from the variation in the figures, where every degree of the sharpness of a curve is obtainable, from a line returning almost upon itself at an exceedingly acute angle, to curves so flat as to present in parts virtually the appearance of parallel straight lines-all this, combined with a knowledge up to a certain point of the nature of all lines cut in glass, makes these rulings more instructive, perhaps, than the markings on diatom valves, about which their is so much question. A curious feature of some of these figures is, that though all the lines would seem to be in the same plane, it sometimes happens that an alteration of focus is requisite to bring out the transverse lines. The same fact has been noticed in observing the transverse markings of the Diatomacea (Journal of the Quekett Microscopical Club, July, 1878).