in the same size, form, appearance, and distribution. I also have given some evidence in an earlier paper, that the neurosomes can hardly be regarded as an artificial product, and so far as modern histological technique is concerned, there is no reason to favor BETHE'S view on this point.

netz.

However, I cannot agree with HELD who thinks that there are two kinds of network, one nervous and the other nonnervous, and that the former may coincide with BETHE'S GolgiHELD'S non-nervous network has been demonstrated by using the molybdenum technique of BETHE. According to HELD, this technique brings out so-called "Gliaschnürringe which send filaments to form the non-nervous network. This point seems to me quite doubtful, for if the Gliaschnürringe as well as the non-nervous or neurokeratin network were stained, one would expect to find neurokeratin structures along the medullary sheath. The latter, however, were not observed by him. My own technique, which is able to stain both neurokeratin and glia, fails to show the existence of the non-nervous or neurokeratin network about the cell-body. One can see frequently the neuroglia fibers which surround the cell-body; these, however, merely pass over the cell-surface and never stop on it. I noticed very often the neurokeratin rings or "Gliaschnürringe" of the medullary sheath in my preparations but was unable to observe any process from these rings such as has been described by HELD. Therefore I am unable to confirm HELD on this last point.

From the above I believe that there is only one kind of pericellular network which is formed by the terminals of the axones, and further, I believe that GOLGI's or BETHE'S network is identical with the network described by HELD as the nervous network from the (1) coincidence or indentical distribution, and (2) from the reticular structure observed in all cases. A different appearance shown by different technique, may be due to the fact that the GOLGI and BETHE methods produce a precipitation of silver chromate and molybdenum salts respectively, which covers the finer meshwork, thus obscuring the internal structure and giving it a coarse appearance.

BIBLIOGRAPHY.

Bemerkungen zu Garbowski's Darstellung meiner Lehre von den leitenden Nervenelementen. Biologisches Centralblatt, 1898, Vol. XVIII, pp. 703-713.

Sur la structure des Cellules nerveuses. Arch. ital. de Biol., Turin, t. XXX.

Das terminale Nervennetz in seinen Beziehungen zu den Ganglienzellen der Centralorgane. pp. 190-214. Monatschrift f. Psychiatrie. Bd. VI.

Ueber die Neurofibrillen in den Ganglienzellen von Wirbelthieren und ihre Beziehungen zu den Golginetzen. Archiv f. mikros. Anat. Bd. 55. PP. 513-544.

Ueber den Bau der grauen und weissen Substanz.
Anat. u. Entwickl. Jarg. 1902. Heft 5-6. pp. 189-224.

Arch.

The Finer Structure of the Neurones in the Nervous

System of the White Rat. Decennial Publications, University of Chicago. 1903, Vol. X.

ILLUSTRATIONS ON PLATE III.

Fig. 1.-Ventral horn cell of a dog.

Fig. 2.-Ventral horn cell of cat.

Iron-haematoxylin.

Fig. 3.-Dendritic branch of ventral horn cell of cat. Iron-haematoxylin.

THE NEUROKERATIN IN THE MEDULLARY

SHEATHS OF THE PERIPHERAL

NERVES OF MAMMALS.

BY SHINKISHI HATAI.

(From the Neurological Laboratory of the University of Chicago.)

With Plate IV.

At as early a date as 1876, EWALD and KÜHNE announced that the nervous system contains a horn-like substance which has a great resistance to chemical reagents and especially to gastric and tryptic digestive fluids. On account of its similarity to the horny material found in other tissues, they termed the substance obtained from the nervous system "Neurokeratin." JOSEPHINE CHEVALIER, in 1884, demonstrated the presence of the neurokeratin in the medullary sheath of the peripheral nerve fibers, by means of chemical analysis. Later (1890) CHITTENDEN again took up the problem of the neurokeratin with Professor KÜHNE, the first investigator of it, and not only confirmed the previous statement of EWALD and KÜHNE, but at the same time cleared up many obscure points. In addition to the chemical determination of it, they showed also that the neurokeratin network in the medullary sheath may be demonstrated under the microscope by treating the fiber with boiling alcohol, ether and digestive fluids. By examining under the microscope the slides thus prepared KÜHNE and CHITTENDEN arrived at the conclusion that there are two layers of the neurokeratin network in the medullary sheath; one closely surrounding the axis cylinder, the other lying immediately beneath the primitive sheath.

Through the investigation of these writers just mentioned, the new field of the study was opened for the neurologist. There are a large number of articles concerning the neuroker

atin, but it is not necessary to review them in detail. Generally speaking, two different opinions are held by the recent investigators; one, according to which the neurokeratin is not a peculiar substance, but an artefact produced by the reagents employed, an albuminous substance (RANVIER) or a nucleoproteid (WYNN). This view is held by several histologists, for instance, ENGELMANN, Gerlach, KÖLLIKER and LAVDOWSKY. The second view, that the neurokeratin is a peculiar substance in the nervous system and preexists as such, is held by most of the physiological chemists as well as by a number of histologists; for instance, LEYDIG, PALUDINO, JOSEPH, SCHIEFFERDECKER, KAPLAN and others.

In recent years the use of WEIGERT'S and HEIDENHAIN'S haematoxylin has given many opportunities to study the structure of the neurokeratin, and as a consequence, a large number of reports have already been made. Most of the recent investigators are inclined to believe in the preexistence of the neurokeratin in the medullary sheath, on both chemical and histological grounds, and moreover the complexity of the neurokeratin increases as the technique improves.

Before discussing the literature further, I shall give an account of my own results.

For this investigation, the nerve fibers were preserved in 10% formalin and cut into sections 10μ thick after the usual paraffine technique. The sections were stained with the "blue solution" and decolorized sufficiently with diluted NH.OH. In some cases the blue solution was used without subsequent decolorization.

1

The preparations thus treated show the double layers of the neurokeratin network in the medullary sheath, one layer closely surrounding the axis cylinder, while the other lies just beneath the primitive sheath as was stated by EWALD and KÜHNE and others.

Such an arrangement of the neurokeratin

1 Preparation of the "blue solution" and its application to the microscopical sections is given in my other paper,-"On the Nature of the Pericellular Network." Journ. Comp. Neurol., Vol. XIII, No. 2, p. 141.