nicellular organisms, reactions of to WEYSSE, A. W. Animal behavior, 174,

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DENISON UNIVERSITY, GRANVILLE, OHIO

Neurology and Psychology.

PUBLISHER'S ANNOUNCEMENT.

Complete sets and separate volumes of back numbers of THE JOURNAL OF COMPARATIVE NEUROLOGY (volumes I to XIII) are for sale at this office at the rate of $3.50 per volume unbound, carriage pre-paid. Single numbers are also sold at prices varying with the contents. The new series began with January, 1904. The price of Volume XIV, now complete, is $4.00 (foreign postage 30c extra). The contents of the last issues follows.

Volume XIV, Number 6, November, 1904.

The Behavior of Paramecium. By H.S. JENNINGS. Seventeen figures.
Editorial. Physiology and Psychology.

Clarence Luther Herrick, with portrait. By H. HEATH BAWden.
Bibliography of C. L. Herrick.

Volume XIV, Number 5, September, 1904.

Retrograde Degeneration in the Corpus Callosum of the White Rat. By S. WALTER RANSON. With one plate.

The Early History of the Olfactory Nerve in Swine. By EDGAR A. Bedford. With fourteen figures.

The Relation of the Chorda Tympani to the Visceral Arches in Microtus. By VICTOR E. EMMEL.

Editorial. Nature Study.

Recent Contributions to the Body-Mind Controversy. By. C. L. HERRICK.
Literary Notices.

Volume XIV, Number 4, July, 1904.

The Associative Processes of the Guinea Pig. A Study of the Psychical Development of an Animal with a Nervous System Well Medullated at Birth. By JESSIE ALLEN. Two plates and twelve figures.

Editorial. Some Unemphasized Aspects of Comparative Psychology.
Literary Notices.

Volume XIV, Number 3, June, 1904.

An Enumeration of the Medullated Nerve Fibers in the Ventral Roots of the Spinal Nerves of Man. By CHARLES E. INGBERT. Thirty-eight figures. Editorial.

Color Vision. By C. L. HERRICK.
Literary Notices.

Volume XIV, Number 2, April, 1904.

Physiological Evidence of the Fluidity of the Conducting Substance in the Pedal Nerves of the Slug-Ariolimax columbianus. By O. P. JENKINS and A. J. CARLSON. One figure.

The Nervous Structures in the Palate of the Frog: the Peripheral Networks and the Nature of their Cells and Fibers. By C. W. PRENTISS. Twelve figures.

The Beginnings of Social Reaction in Man and Lower Animals. By C. L. HERRICK.

Continued on page three of cover.:

Comparative Neurology and Psychology

Volume XV

1905

Number 1

ON THE AREAS OF THE AXIS CYLINDER AND

MEDULLARY SHEATH AS SEEN IN CROSS
SECTIONS OF THE SPINAL NERVES OF VER-
TEBRATES.

By HENRY H. DONALDSON and G. W. HOKE.

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

With one figure.

Introduction.-The results presented in this paper are, in each case, based on averages of the measurements of twenty or more spinal nerve fibers. The nerves were taken from various animals representing the five great classes of vertebrates. The measurements show that the areas of the medullary sheath and enclosed axis are nearly equal, and by consequence that the volume of the substance forming the axis cylinders is equal to that forming the medullary sheaths. The relation constitutes a point of similarity remarkable for its wide extension through the vertebrate series.' It enables us, moreover, to estimate in any nerve the volume of the substance specialized for the conduction of the nerve impulse. Since this quantitative relation between axis cylinder and sheath is so close, it strongly suggests that in some way the axis controls the formation of the surrounding medullary substance.

In the spinal nerves of some animals this relation, as expressed by the equal areas of the axis and sheath when the fibers. are seen in the cross section, was pointed out several years ago

1 The Acrania and Cyclostomi do not develop medullary sheaths on their nerve fibers, and are therefore not included.