Page:Popular Science Monthly Volume 11.djvu/445

Rh  into unlike parts. Thus we have what does not exist in any other tissue—a mechanism of nervous tissue itself, a central nervous mechanism of complex structure and complex function, the complexity of which is due not primarily to any mechanical arrangement of its parts, but to the further differentiation of that fundamental quality of irritability and spontaneity which belongs to all irritable tissues and to all native protoplasm.

In the following pages I propose to consider the facts of physiology very much according to the views which have been just sketched out. The fundamental properties of most of the elementary tissues will first be reviewed, and then the various special mechanisms. It will be found convenient to introduce early the account of the vascular mechanism, and of its nervous, coördinating mechanism, while the mechanisms of respiration and alimentation will be best considered in connection with the respiratory and secretory tissues. The description of the purely motor mechanisms will be brief, and, save in a few instances, confined to a statement of general principles. The special functions of the central nervous system, including the senses, must of necessity be considered by themselves. The tissues and mechanism of reproduction naturally form the subject of the closing chapter.



UBLIC attention has been directed to Jabloshkoff's system of electrical lighting by the use that has been made of it at the Magasins du Louvre, in illuminating a hall recently opened. During the past year this invention was brought under the notice of the public by a communication addressed to the Paris Academy of Sciences, and by an experiment made before the Physical Society. The readers of La Nature are acquainted with the usual methods of producing electrical light, and we here again explain their general principles, with a view to render more intelligible the comparisons we propose to make.

Two carbon-points, borne on suitable metallic supports, are arranged in one line, with their tips in contact. An electric current of high intensity is made to pass into them; they may become heated, but they will not give out light unless they be separated by a little distance from each other. On separating them, by the hand or other-wise, the voltaic arc appears and gives out a very strong light. This light persists, provided the carbons are a few millimetres apart; but,