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paper, by S. Weir Mitchell, M.D., and George R. Morehouse, M.D., of Philadelphia, is a very complete study of the anatomy and physiology of the breathing organs in turtles. It seems that, although at one time, and by a single observer, the true mode of the breathing of these animals was partially understood, it had long been neglected, and modern physiologists have taught that turtles forced air into the lungs as do frogs. Drs. Mitchell and Morehouse have shown that turtles breathe like mammals, by drawing air into the lungs by the aid of muscles situated in the flanks and on the outside of the lungs. Their paper contains a detailed account of the anatomy of the breathing organs of turtles, and is illustrated with numerous wood-cuts. The most novel discovery described by the authors is that of a chiasm or crossing from side to side of a portion of the nerves which supply the muscles of the larynx. Except the well-known facts as to similar crossings within the skull, no previous author has described any similar extra-cranial arrangement of nerves. The physiological uses of the laryngeal chiasm has been fully studied by Drs. Mitchell and Morehouse; and more recently Professor Wyman, led by their discovery, has described similar nerve arrangements in serpents and in certain birds. The authors express their indebtedness to the Smithsonian Institution for the aid with which they were furnished in obtaining the requisite specimens for experiments and for dissection. The following papers have been accepted for publication, and will form parts of the fourteenth volume of Contributions: 1st. Three additional parts of the series of discussion of the magnetic observations at Girard College, by Professor A. D. Bache. 2d. The result of a series of microscopical studies of the medulla oblongata, or the upper portion of the spinal marrow, by Dr. John Dean. 3d. A memoir on the palaeontology of the Upper Missouri, by F. B. Meek and F. W. Hayden. 4th. An account of the photographical observatory and various experiments in regard to this subject, by Dr. Henry Draper, of New York. 5th. A monograph of the “Laridae” or gulls, by Dr. Elliott Coues. All these memoirs, except the last, are in the hands of the printer, or in process of illustration by the engraver. In several of the preceding reports an account has been given of a series of reductions of the magnetic observations made from 1840 to 1845, inclusive, at Girard College, Philadelphia, by Professor Bache. The first two of the papers of this series related to what is called the eleven-year period of the variation of the needle, which corresponds with the recurrence and frequency of the spots on the sun. The third paper relates to the influence of the moon on the variation of the needle. The fourth refers to the change in the horizontal part of the force of the earth's magnetism coinciding with the elevenyear period of the spots on the sun. The fifth relates to the effect of the sun in producing daily and annual variations in the horizontal component of the magnetic force. The sixth relates to the lunar influence on the horizontal magnetic force. A particular account has been given of the result of all these investigations, which tend fully to corroborate the conclusions arrived at from observations in other parts of the world, that both the sun and moon are magnetic bodies, and exert an influence upon the polarity of the earth ; and also that the magnetism of the sun has variations in intensity which are in some way connected with the appearance of spots on its surface, giving rise to the variations in those perturbations of the needle which have been called magnetic storms, and which present a periodical recurrence at an interval of about eleven years. The influence of the moon is much less marked than that of the sun, and appears to be more analogous to the temporary magnetism induced in soft iron. Parts VII, VIII, and IX of this series, now in the press, are a continuation of the same subject. Part VII contains the discussion of the effect of a change of temperature on the readings of the vertical force instrument. If a magnetic needle could be supported perfectly free in space, so as to assume the direction into which it would be brought by the magnetic action of the earth, it would arrange itself in the line of what is called the dip, or the inclination of the needle. At the magnetic equator of the earth such a needle would be parallel to the horizon, but, departing from this line either to the north or the south, the inclination would increase continually until we arrive at the magnetic pole, when it would be vertical. It is plain that the full magnetic force of the earth, in the line of the dip, may be resolved into two. others, viz., a horizontal force, or that which draws the ordinary magnetic needle back to the meridian when it has been deflected from this position ; and, second, the vertical force which tends to draw the end of the needle down into the line of the dip. The fre
quency of vibrations of a magnetic bar suspended by an untwisted thread, so as to be horizontal, gives the horizontal component of the force of the earth, while the vibrations of a similar bar placed in the plane of the dip, and poised horizontally like a scale-beam on two knife-edges, gives the variations in the vertical force. These vibrations, however, will be affected not only by the changes in the magnetism of the earth, but by that in the bar itself; and as the latter is affected by the temperature of the place, a series of observations and discussions was necessary to ascertain the corrections due to this cause. For this purpose the room was artificially heated and cooled; but the value of the correction was finally deduced from an investigation of the whole series of regular observations compared with the changes of temperature indicated by the hourly register of the thermometer. The corrections for temperature were afterwards applied to all the observations. The larger disturbances were then separated from the body of the series in the same manner as had been done with regard to the horizontal force, by which means the effect of the monthly and yearly disturbance of the sun is exhibited analytically and graphically. From the results it appears that the number and aggregate amount of disturbances were least in 1844; that in each year the greatest number of disturbances occurs in March and September, and the least number in June, or, in other words, the maximum about the equinoxes, and the minimum about the solstices. In an appendix to this paper the connexion of the appearance of the aurora borealis with the disturbances of the direction and force of the earth's magnetism is discussed. From the result of this discussion it appears that there is a periodicity of about eleven years in the recurrence of the frequency of the aurora, as well as in that of the great disturbances of the needle, and that these are coincident with each other and with the appearance of the spots on the sun. The eighth part of the series gives the discussion of the daily and yearly variations due to the action of the sun on the vertical component of the magnetic force. The mean variation of the force is determined for each hour during each month and for the whole year, and also for the summer and the winter separately. These are expressed analytically and graphically, and an examination of the curve shows a principal maximum about 1 p.m., and a principal minimum about 9 a.m. There is an indication of a secondary maximum about 2 a.m., and a secondary minimum about 4 a. m.
In summer the curve appears to have but one greatest and one least ordinate occurring about noon and midnight. In winter the double feature of the curve becomes quite conspicuous. The vertical force appears greater in May, June, July, and August, and less in the remaining months, with a range of about a hundred and five hundred thousandth part of the whole force. The ninth part gives the investigation of the influence of the moon upon the vertical force ; also upon the direction and intensity of the total force. The methods of investigation are the same in this as in the preceding parts. The daily effects of the moon exhibit a principal maximum a little before the planet passes the upper meridian, and a principal minimum about three hours after it passes the lower meridian. The average epoch of the tide of vertical force is about one and a half hour in advance, apparently, of the culmination of the moon. A secondary variation of this force, though noticed, is very feeble. The subject of the time of greatest lunar disturbance is yet very imperfectly developed, and more observations in regard to it are desirable. A comparison is also given in this paper between the observations made at Toronto and Philadelphia, and their accordances or differences are stated. The effect of the moon upon the direction and intensity of the total force is obtained by a combination of the vertical and horizontal components. From this part of the investigation it appears that the dip is greatest at 8 and 20 hours, and least at 3 hours and 13%, the range being equal to 3.6 seconds; and also that the maximum strength of the earth is greatest at half-past 12 and 11, and least at 7% and 17 hours, the results, from the observations at Toronto and Philadelphia, being remarkably coincident. The next paper of the foregoing list is that by Dr. Dean, which comprises the anatomy of the medulla oblongata, both human and comparative, from the lowest roots of the hypoglossal nerve, through the upper roots of the auditory, including the hypoglossal, nasal, glossopharyngeal, abducens, facial, and auditory nerves. The objects of the investigation were principally as follows: 1st. To illustrate the topography of the medulla oblongata by means of a series of photographs, which might completely map out all the principal changes in structure as they successively occur, connected with the development of the different nerves, with the details which accompany the development of their nuclei and accessory ganglia. 2d. The study of the more minute histological details, such as the course of the nerve roots, their entrance into their respective nuclei and connexion with nerve cells, the connexion of the nuclei with each other by nerve fibres passing from the roots and from the nerve cells, the structure of the olivary bodies which possess a peculiar interest from their resemblance in convoluted structure to the cerebrum and cerebellum. 3d. An attempt to show, notwithstanding the apparent difference of structure between the spinal cord and medulla oblongata, a difference which appears very considerable at first sight, that the plan of structure of the two is identical, that the general arrangement of parts strictly corresponds, that the relation of the nerve roots to their nuclei or cell groups is the same, and moreover the connexion established between the different nuclei is carried out on the same plan. The illustrations for this work were taken by the author himself directly from the microscopic dissections by photography. For the general edition the photographic illustrations have been copied on stone with great care by L. H. Bradford. The steel plates were engraved by J. W. Watts. Besides these, a limited number of photographic prints from the original negatives have been prepared by Dr. Dean himself for private distribution, and from these negatives other copies may be obtained either on direct application to the author or through the medium of this Institution. This paper, which is the result of over two years of constant study, was referred to Dr. W. A. Hammond, of the United States army, and Professor Jeffries Wyman for critical examination, and was recommended by them for publication as a valuable addition both to human and to comparative anatomy. The third paper accepted for publication is on the Palaeontology of the Upper Missouri, by F. B. Meek and F. W. Hayden. This work contains figures and descriptions of all the known invertebrate fossil remains of the various geological formations of Idaho, Dakota, Nebraska, and portions of Kansas. About 370 species, nearly all of which are new, are fully described, and the descriptions are accompanied by remarks on the relations of each species to allied forms from other districts in this country and Europe, both living and fossil—its geological range, geographical distribution, &c. The illustrations consist of about one thousand carefully drawn figures, occu. pying forty-five quarto plates. In addition to full descriptions of species, the work also contains extended accounts of all the genera to which these fossils belong, with the synonymy of each genus, and remarks on its affinities to other genera, both living and extinct ; and assigns the probable period of