Imágenes de páginas

scientific eminence and moral worth of the deceased. The resolutions were unanimously adopted.

Professor Agassiz gave the result of some of his recent observations on the phenomena accompanying the first appearance of a circulating system in the higher animals. He remarked, that physiologists had hitherto believed that in Vertebrata the circulation commences by the formation of true blood, flowing from a cavity formed by a group of structural cells which unite to form the heart; its currents, which become gradually inclosed by similar structural cells, forming the bloodvessels. The circulating fluid from the commencement had been regarded as true blood. Recent investigations had convinced him that this is not the case. The primitive fluid in the bloodvessels is not blood, but liquid albumen. This fact he had formerly demonstrated in the embryo chick and turtle, and he had recently noticed it in the embryo of the Lophius piscatorius, or Devil-fish. Owing to the transparency of the fluid, the currents were first made out with great difficulty, but, when closely watched, became evident by the separation of particles from the walls of the channels and their circulation in the current, which were distinctly seen. The albumen is that in which the yolk cells of the ovum swim, and the first blood corpuscles are transformed yolk cells. The blood at first contains, besides its proper corpuscles, yolk cells, structural cells, pigment cells, &c. In observing the embryo of Lophius piscatorius, while attentively watching one of the primitive isolated currents during four hours, Professor Agassiz saw blood corpuscles starting, and finally a true blood circulation established, where before there had been merely a transparent fluid albumen moving without granules.

Professor Gray presented a short memoir entitled “Note on the Characters and Affinities of Vavaa, Benth. ; also of Rhytidandra, Gray.This paper was referred to the Publishing Committee.

Four hundred and sixth meeting.

November 8, 1854. — Quarterly Meeting. The President in the chair.

Hon. B. R. Curtis, Hon. Rufus Choate, and Rev. Ephraim Peabody were elected Fellows of the Academy in the Section of Philosophy and Jurisprudence.

Dr. Charles E. Ware was elected a Fellow of the Academy in the Section of Medicine and Surgery.

Dr. Thomas M. Brewer and Dr. Silas Durkee were elected Fellows of the Academy in the Section of Zoology and Physiology.

Dr. B. A. Gould communicated elements of the fourth comet of 1854, determined from observations at Berlin and Cloverden ; – together with the results of some further computations instituted in consequence of the striking resemblance between these elements and those of the first comet of 1845. These results are given in detail in the Astronomical Journal.

Dr. Hayes alluded to the opinion which has been held by some, that after seasons of drought springs flow more freely before rain falls. His attention had been recently called to the subject by hearing, on reliable authority, that in California this phenomenon is observed some weeks before the annual rains. He inquired if any gentleman present could explain it.

Professor Lovering said that in a paper read before the American Association for the Advancement of Science, during the session at Cleveland, this phenomenon had been attributed to variations in atmospheric pressure, such as produce changes in the barometer; and he regarded the explanation as a very rational one.

Dr. Jeffries Wyman stated that he had been engaged in making some experiments with a view to ascertain, if possible, the cause of contractility in some vegetable tissues, as in the capsules of the common Balsam and the Echinocystis lobata. In these it is well known that, when the seeds are ripe, the seedvessel bursts open, scattering them to a considerable distance. It was Dutrochet's theory, that this action is due to the sudden transfer of fluid from the inner to the outer cells of the wall of the capsule. Dr. Wyman had demonstrated the impossibility of this, by dissecting away the outer layers of cells without impairing at all the contractility of the capsule. He had himself come to the conclusion, that the motion is due to the spontaneous contraction of the cells on the contracting side, in the way that motion is produced in the hydroid polyps. In the contracted capsule the cells on the concave side are found to be shortened, while those on the opposite side are elongated. In the Balsam capsule the contraction is so sudden that the shortening of the cells cannot be watched, but in the Echinocystis the motion is so gradual that the change can be observed under the microscope. When gradually subjected to the action of anæsthetic agents, the capsules lose their contractility; but when suddenly placed under their influence, an immediate contraction is the usual result.

Four hundred and seventh meeting. December 12, 1854. — QUARTERLY MEETING. The President in the chair.

Dr. Durkee read a paper on the Common Mosquito, Culex pipiens, giving a description of the microscopic structure of its proboscis, with an account of its development and habits of reproduction.

On motion of the Treasurer, the following vote was passed :

“ Whereas, the American Academy of Arts and Sciences has received notice from the executors of the will of the late Samuel Appleton, that they have transferred to this society stocks amounting to ten thousand dollars, from the fund left for distribution by Mr. Appleton,

Voted, That the Academy accepts with much gratification this contribution to the cause of Science from one who found his happiness in acts of beneficence, and that our thanks are due to the executors of his will for the direction which they have given to his bounty."

Professor J. Lovering made a brief communication, describing new experiments and modes of illustrating the laws of Light and Sound.

“1. At the meeting of the American Association for the Advancement of Science, at Cleveland, in August, 1853, I gave an account of some changes, and, as I believed, improvements, in the construction of Soleil's apparatus for projecting on a screen the chromatic phenomena of polarization. As the volume which is to contain the proceedings of that meeting has been unusually delayed in its publication, and has not yet appeared, I propose to present now to the Academy the substance of my former paper. The apparatus of which I speak, as made by Soleil, is described in Pouillet's Traité de Physique, and elsewhere ; and a sectional view of it is given on Plate XXXIV., Fig. 21, of the book first mentioned. I here present the ap.

Fig. 1.

paratus as I have modified it. Soleil's plan is well adapted to many experiments. If the crystal is small, it is placed near the focus of the large lens, which condenses the light upon it and illuminates it strongly, so that the colored rings, black crosses, &c. developed by the analyzer may be projected upon a distant screen on an enlarged scale. But whenever these experiments are to be repeated with crystals of low crystalline power, as quartz, for example, some modification of the apparatus is necessary. Otherwise, it will be impossible to see anything more than the colored centre without the rings. A more diverging beam of rays is required for the rings. Thus have I been led to the construction of another eyepiece, to be substituted in such cases for that which accompanied the original apparatus. It VOL. III.


Fig. 2. is represented in Fig. 2. The two small lens-

es, L', having with their united forces a focal 00

length of less than an inch, receive the converging rays as they come from the large lens, L, and make them still more convergent. It is

necessary that the quartz should be adjusted very near the focus of the rays, and also that the analyzer should be placed as closely as possible in front of the quartz. Otherwise, this highly divergent pencil of light, after it leaves the focus, will not be able to get through the small area of the crystal and analyzer, and therefore the whole field of view will be curtailed. The crystal and analyzer are held by separate rings, which are supported on uprights which slide independently upon a horizontal bar, and the two rings may, therefore, be pushed as closely together as the thickness of the crystals will allow.

“ In Soleil's apparatus, there is an opening, such as is seen at 0 of Fig. 1, similar to that made in magic-lanterns, and for the same object, namely, the introduction of the frame containing the object to be magnified. When Soleil's apparatus is used for the inspection of large objects, such as pieces of tempered glass or artificial selenite figures, they are introduced at this opening, and in these cases the large lens serves as a magnifying-glass, and there is no condensing lens to help the illumination. This defect would not be felt with very large objects, as large, that is, as the lens itself; because the object itself would receive immediately as much light as the lens could throw upon it. But the objects to be examined are seldom, if ever, of this magnitude. Hence, much of the light which might otherwise be saved, is lost for want of a condensing lens. In order that the ap

paratus may retain all the advantages which belong to it in its original - form, I have retained the opening 0, which may still be used in any cases where it is preferred. But the tube which carries the large lens has been divided at the middle of its length, and one part made to slide in the other. Another opening, O, similar to that in the original apparatus has been joined to one end of the interior tube. By pushing more or less of this tube into the next exterior one, the objects placed in the new opening can be put at smaller or larger distances from the principal lens, which is to this opening an illuminating lens. The best distance, in any given case, is that which makes the section of the cone of rays by the object equal to that part of its own

« AnteriorContinuar »