A Simple Method for Obtaining Synchronized Inductorium Break Shocks.

is in use, the oil connection is easily broken by movement of the mechanical stage, instead of traveling freely with it as happens in using the bevel top. Furthermore, any rapid downward movement of the condenser in focusing, often, and under some conditions usually, br6aks the ifim at one side with the sucking in of a large bubble of air which is then trapped above the lens in the pocket formed by the edge of the raised metal face (Fig. d). This trapped bubble can be removed only by making a fresh immersion. When a condenser with an 8 degree oil-retaining bevel is used, racking the condenser downward, in focusing or in using a thin slide, allows the oil to gather in rapidly and uniformly on all sides, making a thicker layer of less diameter (Figs. b, e). The central body of oil can be drawn out to a surprising distance without breaking. On an upward focusing movement the excess of oil merely makes a larger ring of oil about the cone of the condenser top (Fig. c). It would be well not only to alter the condenser which you are using but also to call the attention of the agent of the microscope manufacturer to this feature whenever he makes his round for orders. was necessary to synchronize break-shock stimulation of muscle by a Du Bois Reymond inductorium, with the time of exposure of short lengths of photographic film mounted on a revolving kymograph drum. The inductorium was actuated through a relay whose cir-c.uit was closed and opened in the usual manner by a contact maker on the axle of the drum. Advantage was then taken of the vertical movements of the horizontal hammer of the inductorium to get only the break shock by the following simple and inexpensive procedure. The hammer of the inductorium was extended about 5 cm by screwing on to it a light strip of brass.. A piece of tough but flexible thread was fixed at the end of this strip and drawn over a light pulley, about 3 cm in diameter, carried on an axle about 10 cm above the inductorium. The free end of the thread was tied onto the head of a 6 penny nail which hung down within a 1 cm diameter glass tube, its lower end dipping into a pool of mercury contained in the tube. One pole of the …