Page:Proceedings of the Royal Society of London Vol 60.djvu/46

38 (c.) The capillary electrometer, a large num ber (about 250) photographic records being taken of the movements of the meniscus. Facsimile reproductions of typical records are given in the fuller communication. The electrometer was used either shunted by a resistance of from 80 to 100 ohms, or in connection with the outer plates of a special condenser, the inner plates of which were connected with the fish or its electrical organ.

The organ responded to m echanical or electrical excitation of its nerves after removal from the fish, the response being unaffected by 1 per cent, curare, or 1 per cent, atropine solution. No response could be evoked by such chemical agents as sodium chloride, glycerine, or weak acid, w hen applied either to the organ or its efferent nerve.

The conclusions draw n by the authors from the experiments on the isolated organ and on the entire uninjured fish maybe summarised as follows :—

(1) The isolated organ responds to electrical excitation of its nerves by monophasic electromotive changes, indicated by electrical currents which traverse the tissue from the head to the tail e n d ; this response commences from 00035" at 30° C. to 0‘009" at 5° 0. after excitation, the period of delay for any given temperature being tolerably constant.

(2) The response occasionally consists of a single such monophasic electromotive change (shock) developed with great suddenness, and subsiding completely in from O002" to 0-005", according to the temperature ; in the vast majority of cases the response is multiple, and consists of a series of such changes (shocks) recurring at perfectly regular intervals, from two to th irty times (peripheral organ rhythm ) ; the interval between the successive changes varies from 0004" a t 30° C. to O01" at 5° 0., but is perfectly uniform at any given temperature throughout the series.

(3) Such a single or m ultiple response (in the great m ajority of cases the latter) can also be evoked by the direct passage of an induced current through the organ and its contained nerves, in either direction heterodromous (i.e., opposite in direction to the current of the response) or homodromous.

(4) The time relations of the response are almost identical whether this is evoked by nerve-trunk (indirect) stimulation, or by the passage of the heterodromous induced current.

(5) There is no evidence th at the electrical plate substance can be excited by the induced current apart from its nerves, i.e., it does not possess independent excitability.

(6) The organ and its contained nerves respond far more easily to the heterodromous than to the homodromous induced current, and the period of delay in the case of the latter response is appreciably lengthened.