QUARTERLY CHRONICLE OF MICROSCOPICAL

SCIENCE.

Histology. TEXTBOOKS.-The third part of the Manual of Histology,' edited by Stricker, has appeared, and contains the following articles:-The Blood-vessels of the Intestinal Canal, by Toldt; the Liver, by Hering; the Larynx, by Verson; the Lungs, by F. E. Schultze; the Kidney, by Ludwig; the Supra-renal Capsules, by Eberth; the Urinary Bladder, by Obersteiner; the Testicle, by La Valette St. George; the Ovaries, by Waldeyer; the Skin, &c., by Biesiadecki; the Serous Membranes, by Klein.

M. Robin has brought out a second edition of his 'Programme du Cours d'Histologie.'

THE BLOOD.-Geinitz (Pflüger's 'Archiv,' No. 1, 1870). has examined the action of hydrocyanic acid on the bloodcorpuscles. If frogs were poisoned with cyanide of potassium or hydrocyanic acid, the blood-discs examined after death showed two remarkable changes. Their shape became rounder, or, in fact, very nearly circular, and their edges became crenulated and granular. The former change predominated when the acid was used, the latter when the salt. In another series of experiments a drop of blood was exposed to the action of hydrocyanic acid vapour in the "moist chamber" of Stricker. The blood-discs first underwent the changes above described, and then dissolved altogether, except their nuclei, the pigment becoming diffused through the liquid. Similar results were obtained with the blood of warm-blooded animals, the discs first assuming the characteristic "mulberry" shape, and then dissolving altogether. These changes are supposed to explain the brilliant colour which blood assumes when treated with hydrocyanic acid, the enlarged corpuscles reflecting more light than in the normal state.

Spontaneous Division of White Blood-cells.-Klein (Med. Centralblatt, January 8th) has observed the phenomena of division, especially in the white cells of the newt's blood. A drop is brought into the moist chamber under the microscope, and kept at a temperature of 25° to 30° C. Two masses may

often be seen marked by a narrow neck of protoplasm, which either reunite to form one cell, or else divide into two, which remain permanently distinct. Another method of division is for a cell to flatten itself out into a disc, from the surface of which arises a kind of mound or elevation, containing a nucleus, which finally separates. The same phenomena were easily seen in the frog's blood, and also in human blood, when kept at a temperature of 35° to 40° C.

TENDONS. Güterbock (Med. Centralblatt.,' January 15th) has repeated the observations of Ranvier on the tendons of young animals, and has come to the following conclusions: -The fissures which are found between the fibrillar bundles of the tendons contain chains of staff-shaped nucleated cells, which may be called connective tissue corpuscles, and which are less numerous in the tendons of adults than in those of young animals. The tendons are so rich in cells as to be little inferior to cartilage in this respect. These chains of cells pass uninterruptedly into rows of cartilage cells, where the tendons are inserted into cartilage.

MUSCULAR FIBRE.-Professor Krause has contributed to the Zeitschrift für Biologie' a paper on the structure of striated muscular fibre, in which he controverts the views of Hensen, which have lately attracted much attention. According to the latter observer, each transverse stria or disc of doubly refracting substance is divided by a disc of less highly refracting substance, which he calls the "median disc." This appearance is regarded by Krause as a misinterpretation of the appearances, and due, at least in part, to the action of water. The median disc he believes to be merely the central portion of the dark or doubly refracting substance, rendered paler by the action of water, and also brought into contrast by the greater distinctness given to the planes of contact of the dark and light substances. Krause has also seen the delicate line crossing the middle of the light substance, described by Hensen, and described also long ago by Dr. Carpenter, from Lealand's preparations (Human Physiology,' 4th edition, p. 296). We are unable now to give a fuller account of this important paper.

LYMPHATICS OF THE EYE.-Schwalbe contributes to Schultze's 'Archiv' (vol. vi, part i, 1870) an elaborate paper on the lymphatic spaces connected with the eye. He confines himself in the present memoir to those of the posterior division of the eyeball. The posterior lymphatic system is defined as including the perivascular spaces of the retina, the perichoroid space with its efferent channels, and, finally, a lymphatic space between the outer and inner sheaths of the optic

nerve, which, without communicating with the other two, opens directly into the arachnoidal sac of the brain.

Between the inner surface of the sclerotica and the outer layer of the choroid is a space, which was recognised by Arnold as a serous cavity, and to which the name arachnoidea oculi might be given. It is, however, occupied in part by some loose connective tissue with elastic fibres and stellate pigment-cells, which constitute the membrana supra-choroidea of Henle, and the lamina fusca of most anatomists. This is quite a distinct structure from the space or sac itself, and need not now be considered. The cavity itself, called by Schwalbe the perichoroid space, has the closest resemblance to the lymphatic sac of the frog, having inner surfaces, which even to the naked eye are sometimes smooth and shining, and are found, on careful examination, to show on both surfaces the epithelial markings characteristic of lymphatic spaces. The principal method made use of to demonstrate this structure was the silver method of Recklinghausen, which had the effect of bringing into view a complete epithelial network, in the meshes of which were contained oval nuclei. No means was found of isolating the epithelial forms, but even without the silver treatment little shreds of membrane containing nuclei could be torn off. These appearances were best seen in the eyes of white rabbits, with more difficulty in pigmented eyes, and not at all in the human eye, since a specimen of this could never be obtained in a sufficiently fresh state. The perichoroid space being thus defined, injections were made into it with the view of determining its extent and connections. When completely filled with a coloured liquid the space was found to reach backward into the neighbourhood. of the entrance of the optic nerve, and forward as far as just under the ciliary processes. The space thus forms a complete double envelope, surrounding nearly the whole of the eyeball. The injection never penetrated into the proper vascular tissue of the choroid, or into any of the chambers of the eye; it did, however, leave the space at four points, and these are points corresponding to the entrance of the venæ vorticosæ. It has been clearly made out that the injection passed through spaces encircling the veins, which, on a cross-section, were found completely surrounded by it. Through these perivascular canals the perichoroid space communicates with the space between the eyeball and the capsule or fascia of Tenon, which may be called the space of Tenon; and this was filled with injection from the perichoroid space. The space of Tenon further communicates backwards by a cylindrical channel surrounding the outer fascia of the optic nerve with

the arachnoid space of the skull. The same methods of investigation as those spoken of above showed that this space is a true lymphatic sac, its internal surfaces being covered with at regular epithelium. The same conclusion has, as is well known, been arrived at by other observers with regard to the arachnoid itself, so that the continuity of the whole system is established. The final proof is given by throwing an injection into the arachnoid, which fills first the canal round the optic nerve and the space of Tenon, then the perichoroid space, and passes at the same time into the lymphatic vessels of the neck, showing the continuity of these cavities with the lymphatic system in general. Beside the canal just spoken of as surrounding the whole optic nerve, to which the author gives the name of supra-vaginal space, there is another included between the two fascia of this nerve, which he calls subvaginal. This is continuous with the arachnoid, from which it may be injected, and surrounds the whole optic nerve almost to its entrance into the eyeball; but here it stops short, not communicating with the proper lymphatic spaces of the eye. Its inner surfaces have the structure of a lymphatic sac, as distinctly as the perichoroid and other spaces.

Schwalbe makes some remarks on the method of investigation by impregnation with nitrate of silver. There can be no doubt that the markings produced on serous surfaces correspond to cell outlines; but he thinks they are caused rather by a precipitation of silver upon the edges of the cells by some albuminous substance adhering to them, than by a staining of any actual cement uniting the cells together. The term endothelia seems preferable, since they are not really identical with ordinary epithelial cells.

LUNG.-F. E. Schultze, in the third part of Stricker's handbook, gives a full discussion of the vexed question of the alveolar epithelium. According to his observations, made principally after injecting nitrate of silver into the air passages, the whole surface of the alveoli and bronchial terminations is in the foetus covered with a continuous and homogeneous epithelium. After respiration is established this epithelium, though not ceasing to be continuous, becomes heterogeneous, and some of the cells, which are originally granular, polygonal, and clearly defined, become pale, transparent, and indistinct, thus producing the appearance of a partial epithelial covering, which has been described by many observers.

MIGRATORY CELLS IN THE SKIN.-Biesiadecki, in an excellent description of the skin, published in Stricker's Hand

VOL. X.-NEW SER.

book,' gives an account of some important observations on migratory cells, which, though published before, have hardly attracted sufficient attention in this country. He describes as of normal occurrence in the deep layer (rete mucosum) of the epidermis, in the corium, and in the subcutaneous connective tissue certain cell forms having the following characters. They are round, oval, or irregular in shape, composed of soft, brilliant protoplasma, with a more or less distinct nucleus, readily stained by carmine, and agreeing generally with the lymph or white blood-cells in form, size, and properties. Being generally met with in the vicinity of bloodvessels, and differing in structure from the regular cells of the part, Biesiadecki regards them as identical with the "migratory cells" first described by Recklinghausen in the cornea, and since then often observed in diseased parts (being, according to other observers, extravasated white blood-cells). The number of these cells met with depends very greatly upon the vascularity or oedema of the skin, and they are enormously increased, especially in the deep layers of the epidermis, in certain pathological conditions. Such cells and their migrations seem to have a more important place in physiology and pathology than has yet been assigned them.

STOMACH.-K. Trütschel ( Med. Centralblatt,' Feb. 19th) has examined the terminations of nerve-fibres in the mucous membrane of the stomach of the frog. He finds in the submucous tissue a fine plexus of delicate fibres, in which cells are here and there embedded. This is in direct relation with nerve-branches, so that the whole must be regarded as a nervous structure. Other nervous filaments, which are not a part of this network, extend in the direction of the mucous membrane, and dividing into smaller branches reach the epithelial layer. In the mucous membrane itself is a layer of large multipolar cells, connected with one another by processes. These are also, without doubt, nervous structures. From these, moreover, nerve-fibres arise, which reach the epithelial layer, and there form a second plexus; while a third similar structure is described as lying immediately under the epithelium. Certain oval, clubbed bodies, which are met with between and among the cylindrical epithelial cells, are regarded as the ultimate terminations of the nerves. The evidence of the nervous character of these different structures rests principally on their coloration by chloride of gold and osmic acid.

LIVER.-Hering, in an account of the liver, published in the third part of Stricker's Handbook of Histology,' repeats his important and now well-known observations on the