Page:Popular Science Monthly Volume 2.djvu/555

From Wikisource
Jump to navigation Jump to search
This page has been validated.

of the nervous and muscular systems devoted to the functions of nutritive life. Electricity by induction, applied to these muscles, causes contraction in them at the point of contact with the poles, while the part situated between the poles remains without motion. Continuous currents produce, at the instant of closing the circuit, a local contraction at the junction with the poles, and then the organ becomes quiet; if it is previously in action, motion ceases. In the case of the intestine, for instance, peristaltic movement is checked; and by means of electricity contractions of the uterus may be suspended in an animal, during parturition. In general, the fluid suppresses spasms of all the involuntary muscles.

All these facts relating to electric action upon the muscles and nerves have been the occasion, particularly in Germany, of laborious investigations, with which are connected the names of Dubois-Reymond, Pflüger, and Remak. The doctrines of these learned physiologists, regarding the molecular condition of the nerves in their various modes of electrization, are still very much disputed. It must be said that they are not supported by any experimental certainty, and perhaps the ideas developed by Matteucci supply better means for the general solution of these difficulties. This eminent experimenter opposed, to the German theories about the electrotonic faculties of the nerves, certain evident phenomena of electrolysis, that is, of chemical decompositions effected by the currents. He supposed that the modifications of excitement in the nerves, brought about by the passage of electricity, depended on the acids and the alkalies resulting from the separation of the salts contained in animal tissues. To this first class of phenomena may be added those electro-capillary currents lately observed by Becquerel. Here must be sought the deeper causes of that complicated and as yet obscure mechanism of the strife between electricity and life.

The effects of electricity on plants have been much less studied, experiments made on this subject being neither accurate nor numerous enough. We know that electricity causes contractions in the various species of mimosa, particularly in the sensitive-plant, that it checks the flow of sap in certain plants, etc. Becquerel has studied its action on the germination and development of vegetables. Electricity decomposes the salts contained in the seed, conveying the acid elements to the positive pole, and the alkaline ones to the negative. Now, the former injure vegetation, while the latter benefit it. Quite lately, the same experimenter has made a series of researches upon the influence of electricity on vegetable colors. Employing strong discharges obtained from friction-machines, he has noticed very remarkable alterations of color, usually due to the rupture of the cells containing the coloring-matter of the petals. This matter, freed from its cellular covering, disappears on simply washing with water, and the flower becomes almost white. In leaves showing two surfaces of diff-