of its cells as compared with twelve newly-charged cells, and also the condition of each individual cell, points often of much practical convenience in an Hospital Electrical Room. [9] A little care is needed to regulate the vibrating needle. The spring should but _barely touch_ the hammer, the adjustment being almost entirely regulated by the protrusion or retraction of the needle by the action of its screw; and the _slightest twist_ of this screw will be sufficient. When the vibration is uneven or stops, and careful manipulation of the needle fails to re-establish it, remove the needle and clean its point as directed in the text. LECTURE II. METHODS OF APPLYING ELECTRICITY. GENTLEMEN, [SN: Résumé of First Lecture.] In our first Lecture we studied the different kinds of electricity employed in medicine, and the construction and management of batteries. I reminded you that we made use of three kinds of electricity; firstly, of friction or static electricity, _Franklinism_; secondly, of the electricity of chemical action, _Voltaism_, or _Galvanism_; and, thirdly, of induced electricity, _Faradism_:--that there had been certain difficulties in the employment of Franklinism, but that these difficulties no longer existed; that Voltaic electricity was electricity in motion, or current electricity, but that while its current (unless artificially interrupted) was always _continuous_--flowing, that is, in an unbroken stream--and from the positive to the negative pole, until the battery was exhausted--it by no means followed that it was _constant_, that is, that it did not vary appreciably in power during application; that only batteries supplying a fairly constant current were fitted for medical use, and that all others should be rejected. We then considered different batteries, both fixed and portable; that while large fixed low tension batteries were unquestionably superior in their therapeutic effects, patients unfortunately were not always movable, and that a portable battery became, therefore, a _sine quâ non_; that portable batteries might be conveniently divided into two classes, one in which electricity was generated by the elements being immersed in an exciting fluid only during actual use, and being taken out of the fluid immediately after use; and the second that in which no removal of the elements was necessary; that the Voltaic current was graduated into doses by some arrangement determining the number of cells to be employed in each case, but that this method, while practically useful and sufficient, failed to convey an exact idea of a measured and unvarying quantity of electricity; and that it had been contended that by the use of a galvanometer, doses of electricity might be as accurately administered as so many grains or minims of ordinary medicines, but that, perfect as the theory might be, I had personally failed to obtain help in practice from a galvanometer; that next in importance to a method of