Page:Proceedings of the Royal Society of London Vol 1.djvu/473

Rh from milk than the cardiac portion of the stomach. The cardiac portion of the stomach of the hawk was found more powerful than the same part of a common fowl.

The gastric glands were carefully dissected out from behind the membrane that lines the cardiac extremity of the tomach of a turkey; and of these, forty grains, by weight, were taken, and their effect compared with an equal weight of membranous lining of the same cavity, an equal weight of membrane from the fourﬂr cavity of a calf’s stomach in a recent state, and forty grains of dry rennet. Since the last must have been prepared from about four times its weight of re- cent membrane, its effect was produced in much the shortest time. The coagulation effected by the gastric glands took place nearly at the same time as by the recent calf’s stomach; while that from the lining of the turkey’s stomach was nearly three times as long in producing the corresponding effects.

From these experiments, the author infers that the secretion from the gastric glands possesses the power of coagulating milk, and com- municate that property to adjacent parts, by which it is imbibed.

The author, having been for some time past engaged in a course of experiments on the refractive and dispersive powers of different substances, the details of which are intended for future publication in a separate work, conﬁnes himself, at present, to a relation of such of his results as have most of novelty or importance. After repeating the experiments that have been made by others on the properties that light acquires by transmission through Iceland-spar, and upon the corresponding properties of reﬂected light originally discovered by Malus, and by him termed polarization, Dr. Brewster observed a singular appearance of colour on each side of a luminous object, viewed through a thin slice of laminated agate. Upon examination of these coloured images through a prism of Iceland-spar, this light was found to be similarly polarized, so as to appear or disappear accordingly as the laminae of the agate were parallel or transverse to the principal section of the spar. He found also that the colourless light transmitted directly through the agate, and from which the coloured rays had been separated, was polarized as well as the coloured rays, appearing and disappearing alternately with them during the revolution of the spar. And accordingly when light previously polarized by reﬂection was received upon the agate, its transmission or reﬂection depended on the relative position of the laminae of the agate to the plane of reﬂection; for when these were at right angles to each other, no light whatever was transmitted.

In the same manner light polarized by transmission through the laminated agate, manifested the usual properties of light so affected by other means.