profession should be made acquainted with the advanced views held by the distinguished author, and that American medical students should imitate the enlightened ideas of theory and practice which he teaches with such remarkable success. It is not too much to say that no physician's or student's library can be complete without this admirable guide. In the next number of this Journal we propose to review the work at length. For the present, therefore, we simply desire to call attention to its appearance, and to commend the excellent manner in which the translators, Drs. Humphreys and Hackley, have performed their part.

THE last publication of the Sanitary Commission is a valuable contribution to anthropology and military science.' It is entirely statistical in character. The nativity of the United States soldiers, their age, weight, pulmonary capacity, mean proportions, and dimensions of trunk and head, etc., are given in the minutest details. As a work of reference to the physiologist and physician, it is of great importance. Its data will prove of use to every one who has occasion to examine the effects of dif ferent climates upon vast numbers of men; the effects of long marches, etc., upon the physical condition and morale of soldiers; and in fact to every one who is anxious to see the physical characteristics of his country's defenders submitted to the searching analysis and exact study of figures.

THE progress of any particular branch of science necessarily leads to researches and discoveries in those other branches more nearly allied; and it is wonderful what rapid strides have

special permission of the author, by George H. Humphreys, M. D., etc., and Charles E. Hackley, M. D., etc., in two volumes, 8vo, pp. 731, 770. New York: D. Appleton & Co., 1868.

1 Investigations in the Military and Anthropological Statistics of American Soldiers. By Benjamin Athrop Gould, Ph. Dr., Member of the National Academy of Sciences; President of the American Association for the Advancement of Science; Member or Correspondent of the Academies or Scientific Societies of Boston, Cherbourg, Göttingen, Marburg, New Orleans, Philadelphia, etc.; Associate of the Royal Astronomical Society of London, etc.; Actuary of the United States Sanitary Commission. New York: Published for the United States Sanitary Commission, by Hurd & Houghton. Cambridge: Riverside Press, 1869, 8vo.

been made in the branches of therapeutics and toxicology. Indeed, since the discovery and introduction of alkaloids, toxicology has become a science, important, and nearly perfect; and it is with pleasure we peruse a treatise' devoted to toxicology in jurisprudence, and inquiries into the toxicological properties of food, air, etc., in detail. To the physician, no less than the chemist, the questions in medical jurisprudence relating to toxicology have ever presented unusually interesting features; and yet, so subtile are the effects of some of the new alkaloids, so minute their fatal doses, and so rapidly are they absorbed into the system, that detection often becomes impossible. This treatise is an answer to a budget of questions on the subject propounded to our author by the Russian Government, elaborated in the highest degree for the use of physicians and advanced students. A knowledge of the simpler chemical laws is presupposed. As a work on toxicology, it has, we think, no equal, but can only express regret that the right of translation is for the present reserved.

2

A NEW attempt toward the compilation of a complete encyclopædia is being made under the editorial supervision of Mr. L. Colange. Several numbers have been issued, and give promise of fulfilling a want which has long been felt. The articles relate to all departments of science, are short, at the same time not meagre, and are generally fully up to the present advanced stage of human progress. If the subsequent performance equals what has already been done, the publisher will have conferred a great boon upon those who, wishing to know something of almost every thing, find it impossible to enter into the full details of a complete study. The work is issued in good style, and is placed at a price which puts it within the reach of all.

1 Die Gerichtlich chemische Ermittelung von Giften in Nahrungsmitteln, Luftgemischen, Speiseressen, Körpertheilen, etc. Von Dr. Georg Dragendorff, Professor der Pharmacie an der Universität Dorpat. St. Petersburg, 1868.

'Zell's Popular Encyclopædia and Universal Dictionary. Edited by L. Colange. Philadelphia: T. Elwod Zell.

CHRONICLE.

I.

PHYSIOLOGY AND PATHOLOGY OF THE BRAIN AND NERVOUS SYSTEM.

Velocity of Cerebral Functions.-The " Archives des Sciences" for April 15th contains a paper by Dr. Adolph Hirsch, on M. F. C. Donders's experiments to determine "the velocity of the psychical functions of the brain," as detailed in the "Archives de Reichert et du Bois-Raymond," and we extract from it the following passages:

"We know now that the brain requires about fifty-thousandths of a second to distinguish and signalize the distinction between two colors, and only fifty-thousandths of a second to distinguish between two vowels which are pronounced. What is more, M. Donders has succeeded in separating these two psychical acts into their components, and he has found that the brain employs about th of a second to recognize an impression, and of a second for an act of volition to signalize that the impression has been received. With regard to the rapidity of perception in cases of hearing, sight, and touch, and the duration of the functions of the cerebral organ, M. Hirsch observes: 'I endeavored to reply to the first of these questions in 1861, and the results which I obtained for the physiological times of the different sensations have been since confirmed by eminent physiologists, among them M. Donders, who gives as the mean of his experiments for touch, 4th of a second; for hearing, th; and for seeing, 4th. But this physiological time, as I have named the interval between the excitation, and the signal given by the manifestation of perception, comprehends a greater number-M. Donders has enumerated not less than a dozen of acts, and divers functions of the senses, the peripheral ganglia, the nerves, brain, muscles, etc., almost all have to be accomplished in this small fraction of a second. It was important to separate as far as possible these different acts, and especially to fix the time employed in the functions of the brain, for which only a maximum limit of th of a second was known, obtained by deducting from the total physiological time the portion employed in transmission by sensor and motory nerves. But what was the minimum limit?'"

M. Donders conceived the happy thought of intercalating, in the series of functions comprised in the physiologic time, certain fresh terms of purely psychical action; and this retardation, evidently due to the intercalation of a new act of the brain, has made us acquainted with the duration of the latter.

M. Hirsch thus describes M. Donders's apparatus: "The noematachograph is composed of a cylinder somewhat like that of the phonautograph, on which time is registered by means of a diapason making 261 vibrations in a second, and moved by electro-magnetism, on the principle proposed by Helmholtz. These vibrations can be divided into fifths, and thus thousandths of a second obtained. The time at which the action which produces a sensation occurs is registered by the machine, and likewise that of the sensation experienced by the power experimented upon.

"The mode of accomplishing this varies according to the means of excitation employed. When an inductive current is used to give a slight shock or prick to any portion of the body, or to light up suddenly different letters, or when the spark is observed through colored glasses to produce the sensation of different colors, the current itself makes its own registry by a spark passing between the style of the diapason and the cylinder, through a sheet of blackened paper, in which it makes a little hole. The observer registers his perception by touching a key, which causes a style to mark the cylinder. To avoid the error introduced by the variable time taken by electromagnets in attracting their armature, M. Donders prefers a purely mechanical signal. The person under observation turns aside a horizontal bar of wood carrying a point, which marks the cylinder. By holding this indicator between two fingers, and turning it right or left, two signals can be given to express different sensations.

"In experiments on hearing, the sound produced by a spring striking a pin springing from the cylinder, or by a diapason put into sudden motion, or by the human voice, is registered by the phonautograph, or by a modification of König's stethescope, over which an elastic membrane is stretched communicating by two caoutchouc tubes, with two embouchures. One of these serves to transmit the sound which is to be perceived, and by the other the patient reproduces the sound he hears, so that the phonautograph registers both at the same time below the chronoscopic line of the diapason. Acting alternately upon the same excitation, by the hand and the voice, we can determine and eliminate the dif ference of time in the two kinds of signalling."

The above descriptions are not very clear; but, in default of better, we lay them before our readers. M. Hirsch continues his paper by describing M. Donders's experiments:

"It was first desired to find the time necessary for discriminating betwen two sensations of touch, and to express the distinction by different signals. To accomplish this, two sim

ilar electrodes were placed on the feet of the patient, and, by means of Pohl's permutator, a slight electric shock was given to the right foot or the left, and the patient signalled his perception by the hand on the same side. The experiments were made under two conditions-either the patient knew beforehand which foot would be operated upon, so that he could give the signal without waiting for reflection, or he did not know on which side the shock would come. In the latter case the physiological time was prolonged to the extent of onefifteenth of a second, and that is evidently the time necessary for an observer to take notice of the side on which he was struck, and, to coördinate with this idea the act of volition, to give the signal with the corresponding hand.

"In a similar manner M. Donders added to the sensation of sight an alternative of perception and volition, by asking the patient to make his signal with the right hand when he perceived an object suddenly illuminated with red light, and with the left hand when it was lit up with white light. In this case the psychical action prolonged the physiological time occupied in the perception of light 0.154s. A similar result was obtained when the person experimented upon pronounced a letter suddenly exhibited to him. If the alternative was only between two letters-a and i, for example-the time occupied by the psychical act was 0.166s., calculated as a mean, and 0.124s., reckoned by the minima. When one out of five vowels had to be distinguished, the time was longer: 0.170s. in the mean, and 0.163s. if the minima were taken.

"Analogous experiments were made with hearing, by uttering a vowel-sound, which the patient repeated as soon as he heard it. Sometimes the vowel to be employed was made known beforehand, and at others not. When a distinction had to be noticed between two vowels, the psychical time was 0:056s. reckoned as a mean, and 0.062s. reckoned by minima; and, when five vowels were employed, the time was 0.086s. according to means, and 0.067s. according to minima.”

In experiments with two colors, the discriminating signals were made with the hand, and by the voice with the vowelsounds; this caused the times in the former case to be a little longer than in the latter. M. Donders found that when the signal consisted in pronouncing the single vowel i, the time was less than when pi, ti, ki, had to be said. The retardation caused by p was 0.011s., by t 0.022s., and by k 0.021s.

It was found that the sense of sight required nearly three times as long to distinguish between two letters as the ear re quired to distinguish between two vowel-sounds. "M. Donders tried with success to separate the time required to distin