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 communication between the arteries and veins, thus supplying the completing link to Harvey's work within a few years after our great countryman's death. On such a foundation of exact knowledge the further pursuance of the subject was one for the Physicist and Chemist, and by them it has been brought to a high pitch, when once the nature of the machine they had to deal with was clearly defined. Observation and experiment were profitably occupied when anatomy had cleared the ground.

It was not only with the functions of respiration that Malpighi's great work on the investigation of tissue structure was concerned. His labours added to, and developed by the famous Dutchmen, Van Leeuenhoek, and Swammerdam, as well as by the Englishman, Robert Hooke, rendered possible the satisfactory examination of the other functions, though the difficulties of the necessary observation and experiment were greater than they were in respect to the circulation and respiration. Connected with the latter, questions of a mechanical and chemical character arose more capable of being answered as the sciences of physic and chemistry were at the time being better understood. While it was comparatively easy to see the movements of the heart and of the lungs in a living animal when these organs