Page:Popular Science Monthly Volume 59.djvu/91

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By Professor G. N. STEWART.

EVERY year a mass of original work in physiology, covering from ten to fifteen thousand pages, for the most part of formidable size and closeness of print, is collected in the various special journals of the science, or mingled with kindred, though miscellaneous, dust in the transactions of learned societies, or decently buried at the public expense in government bulletins and official reports. Those four hundred square yards of printed matter embrace, on the average, more than five hundred papers in German, English, French and Italian, without reckoning stray messages in less familiar tongues, such as Russian, Polish, Dutch, Spanish, the Scandinavian languages, the dog Latin of graduation theses, and even, it may be Japanese, Arabic and modern Greek. The great majority of these communications either contain new facts or are directed, often with notable acuteness, to the unfolding of new relations between facts previously established. It is obvious that no survey of recent physiology which is possible within the space at our disposal could pretend to exhaust the contents of its crowded archives even for a single year. I shall try rather to trace the main tendencies, while incidentally mentioning some of the outstanding achievements of recent physiological discussion and research, than to enter in any detail into the results of particular investigations. Foremost among these tendencies is the study of the structure and functions, and especially the chemical and physico-chemical relations of the individual cell, in which, as has been well said by Bunge, in his brilliant Lectures on Physiological Chemistry, lies ever the riddle of life. While the mode of action of the complex physiological mechanisms, built up by the grouping and chaining together of cells of the same or of different kinds, deserves and has attracted the most assiduous attention, it has become more and more apparent that, as we push our enquiries back, we are always, sooner or later, arrested at the boundary of the cell. We attempt, for example, to explain the mechanism by which the circulation of the blood is maintained and regulated, and up to a certain point we succeed tolerably well. We recognize as the central factor the rhythmically contracting heart which forces the blood through the branching arteries into the netted labyrinth of the capillaries, whence it is again conveyed to the heart by the veins, and thus completes its destined round. We know that the rate and force of the heart-beat and the caliber of the blood vessels are controlled by efferent nerves carrying impulses down to them from centers situated in the medulla oblongata, the portion of the central nervous