nated with flour dust, and, on inquiry, he learned that the boy's father was a pastry-cook.

The difficulties which are involved in the study of bacteria arise partly from the gaps which appear in the classification of these minutest of all living organisms and the new forms which are continually cropping up, and partly from the microscopes employed, although furnished with high powers, possessing little power of illumination and definition, whilst the investigation of bacteria is a matter of enormous difficulty on account of their extreme minuteness, their weak refracting power, and their motion. By Dr. Koch's process, however, photographs of bacteria will be obtained showing not only their contours, but any flagella or other details, and thus correcting the false ideas founded on erroneous drawings, and paving the way to fresh discoveries. It is confidently predicted that in many kinds of pathogeny where a morphological distinction cannot be discerned, but which are the cause of complaints of a most diverse nature, there will be quite characteristic differences discovered.

Dr. Haupt speaks in the highest terms of Dr. Koch's method, but says that for the practical physician it is too tedious and troublesome. His modification if it consists in staining the whole fluid which contains the bacteria, instead of each preparation by itself. This involves but little expenditure of time and trouble, and can be done at the patient's bedside or at the dissecting table if he be provided with a bottle in which to put the substance to be stained, and another containing the staining fluid. The microscopical examination may be subsequently made at any convenient time, and the bacteria are as clearly seen as when Koch's method is used.

The fluids which Dr. Haupt employed were carmine, eosin, rose de Magdala, hæmatoxylin, parme, anilin-violet, fuchsin, and erythrusin, and, except with the first two, he obtained good results. Hæmatoxylin stained Micrococcus very quickly. He recommends as best anilin-violet, fuchsin, and especially erythrusin.

Bacterium termo, though difficult of preparation, should be first experimented with, as what answers with it will succeed with all bacteria. Bacterium termo is easily procured by exposing a piece of raw meat placed with water in a porcelain cup to the sun for an hour or two, or letting it stand near a warm oven. When an opal-like scum has formed on the fluid, every drop is seen under the microscope to contain millions of these bodies.

This or any other fluid containing bacteria (urine, serum, blood, &c.), should be put in a 10-gramme glass which has been carefully washed and rinsed with alcohol. The bottle should be a fourth or a fifth part filled, and the same quantity of a solution in water (well filtered) of the staining material added, and then, after being well shaken, it is to be corked and labelled. It is well to write on the label its contents, date, and hour. With some objects the staining is effected in five, ten, or fifteen minutes, others require twenty-four to forty-eight hours. After being assured by examination with the microscope that the result is satisfactory, a drop is then taken by means of a pipette from the bottom, and spread out well on a glass

slide and dried in a warm place (well protected from dust), which takes about ten or fifteen minutes. A drop of dammar varnish or Canada balsam is added to it, and the covering glass pressed down as much as possible. The preparation is then ready.

As compared with preparations made by Dr. Koch's method, the ground appears a little more coloured. Since, however, the bacteria are considerably darker, and as high powers must necessarily be used, in which case the colour of the ground causes no inconvenience, the method is strongly recommended to those who have a limited time to devote to microscopical manipulating.*

A Mineralogical Microscope.-M. Renard describes, in the Bulletin of the Belgian Microscopical Society,' a new microscope intended for the examination of microscopic crystals by polarized light. One of the leading pecularities of its construction consists in the contrivance (apparently adopted for economical reasons) by which the objective is centered upon the object on a rotating stage. The tube of the microscope carrying the object-glass is enclosed in a fixed outer tube, which is contracted at the upper part so as not to allow of any "pivoting" of the inner tube at that end. Below the contracted part there is a space between the outer and inner tubes, the former being lined with parchment, which is pressed against the latter by springs. Through the lower end of the outer tube work two screws at right angles to each other, which press against the inner tube and move it in two rectangular directions (or any intermediate one), so that it can be readily brought into the correct position.

Alcoholic Fermentation.-An interesting series of experiments was lately instituted by Herr Muntz, in order to determine whether the living cells of the more highly organized plants, when entirely cut off from oxygen, are equally able with the cells of fungi to produce alcoholic fermentation. For this purpose he experimented with a variety of plants, beet, maize, cabbage, chicory, portulacca, nettles, &c. From each kind three equally healthy plants were selected. One was left in the open air, and the other two were placed, with the accompanying soil, under capacious bell-glasses containing an atmosphere of nitrogen, the oxygen being removed by pyrogallic acid. After a lapse of from twelve to forty-eight hours, they were removed from the glasses. One was placed in the open air in order to be certain that the power of development was retained after the imprisonment, and the other was cut off above the ground, distilled with water, and tested for alcohol. In all cases the plants which had been in an atmosphere free from oxygen showed appreciable quantities of alcohol, amounting often to a thousandth of the entire weight of the plant, while no traces could be detected in the plant which had remained in the air during the same time.†

Alcoholic Fermentation.-M. Berthelot recently published, in the 'Revue Scientifique,' what purported to be a copy of some notes (written in October 1877), which were found after his death amongst the papers * Zeitschrift für Mikroskopie,' vol. i. p. 175.

Nature,' vol. xviii. p. 504.

of the late Claude Bernard. These notes, to quote M. Pasteur's words, “are an absolute condemnation, without any restriction, of my views on the subject of fermentation in general, and alcoholic fermentation in particular." M. Pasteur took the matter up with some warmth, and the Comptes Rendus' of 22nd and 29th July contain two communications which he made to the Academy, together with the rejoinders of M. Berthelot. M. Pasteur considers he has established that the notes of M. Bernard refer to experiments only just commenced, and which Bernard intended to repeat and check. This view M. Berthelot does not appear to controvert. M. Pasteur concludes by saying that "he is resolved to repeat the experiments of Claude Bernard, and that on a scale and with a fulness of results worthy of the subject and the respect due to the deceased. M. Berthelot applauds this resolution, and anticipates beneficial results to science, "which lives by observations and contradictions. Since the dis

coveries of M. Pasteur have fixed our ideas of the origin and multiplication of the organized beings which propagate fermentations, a new problem has been presented. The point is to know whether the chemical change produced in every fermentation is not resolved into a fundamental reaction, excited by a definite special principle of the order of soluble ferments, which in general consumes itself proportionately to its production-that is, transforms itself chemically during the very accomplishment of the result which it causes. To recognize such a ferment, we must know how to isolate it; that is, to ascertain the special conditions under which the soluble ferment is secreted in a greater proportion than it is consumed.

The definite relation between the soluble ferment and the microscopic being which forms it has been pointed out, I believe, for the first time with precision, in my researches on the inverting ferment contained in the cells of beer-yeast. It has been found since in the ammoniacal fermentation of urea and elsewhere. It may be well to examine now whether it can be extended to alcoholic fermentation itself —that is, whether some particular condition can be discovered such as those which Claude Bernard seems to have perceived-a condition in which the matter which provokes the alcoholic decomposition of the sugar is formed in an excessive proportion, and consequently capable of being isolated. Alcoholic fermentation would then, as is the case already with most of the others, be brought back to the purely chemical actions."

The Structure of the Brain in different Orders of Insects.-The Supplementary vol. xxx. of Siebold and Kölliker's Zeitschrift für Wissenschaftliche Zoologie,' contains an elaborate article by J. H. L. Flögel, illustrated by a number of microphotographs. This and Dietl's excellent paper, published in 1876, are the only treatises on the minute structure of the brain of insects, Owskianikof having studied that of the spiny lobster Palinurus several years ago, while Dietl studied the brain of Astacus. Flögel establishes three points as the results of his researches.

First, the constant presence of the remarkable central body in the mature insects of all orders, while it is almost absent in the larvæ of

Lepidoptera (but not in Hymenopterous larvæ). We are thus led to suppose that it has something to do with the formation of the faceted eyes. If it has any relation with the bundle of fibres passing from the optic lobe, there is nothing to indicate it.

Secondly, the size of the olfactory lobe, with its olfactory bodies, correlated in insects with small antennæ entirely unfit for tasting, but on the contrary, with a very completely developed sense of smell, is in the author's opinion an excellent proof of the correctness of Leydig's view that the antennæ are organs of smell, whatever may be brought forward in opposition to it. If they are to be interpreted as an apparatus for detecting sounds, we, on the other hand, are acquainted with the finer structure of the organs of hearing in the Orthoptera, and know that they have no such constituted brain-centres as the olfactory lobes.

Thirdly, Flögel draws attention to the wonderful and so little understood facts that in insects, where the lobes ("bechers" of Flögel, "lappen," "gestielte körper," &c., of Dietl) and the substance around them (gerüst) constitute the greater part of the brain, there is indeed no connection of the nerve-fibres to be found with the remaining parts of the brain, and consequently also with the oesophageal commissures. The opinion that the ganglionic cells are in direct relation through fibres with the organs of the body is provisionally unfortunately contradicted. But where are the intermediate stations? he asks.

Finally, the author claims that the essay indicates the outlines of a future brain topography for insects, and shows that the single parts of the brain have their homologues in the different orders of insects; consequently a ground-plan in the organization is not to be mistaken, and thus a comparative anatomy of the brain of insects is outlined comparable with that of the vertebrates, as established by the researches of Stieda.*

The Movement of Microscopic Particles suspended in Liquids.-In Section A. (Mathematical and Physical) of the British Association's recent Meeting, the following paper, entitled 'Note on the Pedetic Action of Soap,' by Professor W. Stanley Jevons, was read:"Since the publication in the Quarterly Journal of Science' for April, 1878, of my paper on Pedesis, or the so-called Brownian movement of microscopic particles, it has been suggested to me that soap would form a good critical substance for experiment in relation to this phenomenon. It is the opinion of Professor Barrett and some other physicists, that the movement is due to surface tension, whereas I believe that chemical and electromotive actions can alone explain the longcontinued and extraordinary motions exhibited by minute particles of almost all substances under proper conditions. Soap considerably reduces the tension of water in which it is dissolved, without much affecting (as is said) its electric conductibility. If, then, pedesis be due to surface-tension, we should expect the motion to be killed or much lessened when soap is added to water.

Having tried the experiment, I find that the result is of the

* 'American Naturalist,' vol. xii. p. 616.

opposite character to what Professor Barrett anticipated. With a solution of common soap the pedetic motion becomes considerably more marked than before. I have observed this result not only with china clay and some other silicates, but also with such comparatively inert substances as the red oxide of iron, chalk, and even the heavy powder of barium carbonate. The last-named substance, one of those which we should least expect to dance about of its own accord, gave a beautiful exhibition of the movement when mixed with a solution of about 1 per cent. of soap, and viewed with a magnifying power of 500 or 1000 diameters.

The correctness of this result was also tested by observing the suspending power of solutions of soap-solution compared with water. If a little china clay be diffused through common impure water, that, for instance, of the London Water Companies, the greater part of the clay will soon be seen to collect together in small flocks and fall to the bottom in two or three hours, the water being almost clear. However, if about 1 per cent. be dissolved in the water, the behaviour of the clay is quite different. The larger particles soon subside, but the smaller ones remain diffused through the liquid for a long time, giving it a milky appearance, quite different from the flocky and grainy appearance of the common water; if 1 per cent. of sodium carbonate be dissolved in common water, and china clay be mixed therewith, the subsidence of the clay is still more rapid, owing, as I have explained, to the increase in the electric conductivity of the fluid, and the consequent decrease of the pedesis. But I now find that if soap be added at the same time, pedesis is not destroyed, but considerably increased, and the clay remains a long time in suspension, two or three days at least.

These facts give a complete explanation of the detergent power of soap. It has long seemed to me unaccountable that for cleansing purposes the comparatively neutral soap should be better than the alkaline carbonate by itself; we are told that the alkali is but feebly combined with the stearic or other fatty acids. But why combine it at all if we need only the alkaline power of the base? The fact is, that 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. If alkaline salts be added, dissolved in water, it becomes capable of acting upon oleaginous matter, but the pedetic power is lessened, not increased. But if the soap be added also, we have the advantage both of the alkali dissolving power, and of the pedetic cleansing power. At the same time we have a clear explanation why silicate of soda is now largely used in making soap; for I have shown, in the paper referred to, that silicated soda is one of the few universal substances which increase the pedetic and suspensive power of

water.

I believe that the detergent power of soap and water is one of