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PROCEEDINGS OF THE PHYSIOLOGICAL SOCIETY

A useful apparatus in the laboratory is the high speed shaking machine. Most of the designs which are at present obtainable commercially are of too light construction and suffer from too many (mechanical) defects to be capable of really efficient and prolonged service. Usually they possess some form of belt drive which slips or breaks in use. Their greatest fault lies in the entire lack of mechanical balance, with the result that the vibration of the entire apparatus is so great as to cause annoyance to other workers in the laboratory. To avoid some of these defects we designed a shaking machine which embodies the best features of automobile engineering as evolved in the horizontally opposed twin cylinder engine. Since the rotating and reciprocating parts are individually and collectively balanced, the machine can be run at very high speeds with very little vibration.. The machine which is shown in the accompanying illustrations is therefore suitable for the preparation of strong colloidal solutions in which very violent shaking is required. An advantage of the design is that the apparatus can be built up in any laboratory from commercially obtainable parts, since the crank-shaft connecting rods and flywheel are those of a Douglas Motor Cycle engine. The crank-shaft runs on caged ball bearings which are supported on suitable pillars. The bottles, which may be of any size found most generally useful in the laboratory, contain equal weights of fluid, and should be balanced against each other. If it is desired to use one bottle only for the solution, the second bottle should be filled with an equal weight of water. The bottles used in the apparatus illustrated held 750 cubic centimetres. In most laboratories Winchester quart