Page:Popular Science Monthly Volume 14.djvu/417

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What Medicine owes to Galileo.—In a lecture on the history of instruments of precision in medicine, a synopsis of which is published in the Medical Record, Dr. S. Weir Mitchell gives to Galileo Galilei the credit of having contrived the first instrument of this kind, viz., the pulsilogon. Desiring to apply some test of the regularity of the swing of the lamp-pendulum in the Pisa cathedral, he is said to have used that most wonderful of clocks, the pulse, for that purpose. This was a grave moment in the history of medicine—"the birth of precision," says Dr. Mitchell. From this use of the pulse as a test of the regularity of the pendulum he was led to use the pendulum as a measure of pulse-rate—thus making the pendulum a pulsilogon. The method of using it was most ingenious. Having always a pendulum of equal weight, he set it swinging, and then shortened or lengthened the string until the beats corresponded with those of the patient's pulse. Then he measured the length of the string, and one person's pulse would be represented arbitrarily but most precisely by say ten inches, another's by eight inches, and so on. Galileo seems to have given little thought to the perfection of this instrument, and does not speak in any of his essays of the medical use of the pendulum. Many years later Sanctorius described an instrument for measuring the pulse which was in no respect different from that of Galileo, and which was called by the same name—pulsilogon.

Plant-Respiration.—From experiments made by Mr. J. Jamieson, and published in Nature, it would appear that fresh sections of many fruits and other vegetable structures, as potato, give the. characteristic reactions of ozone, viz., causing separation of iodine from iodide of potassium, and turning tincture of guaiacum blue, the intensity of the reactions depending mainly on the comparative freshness of the fruits and vegetables. Mr. Jamieson further finds that these structures contain a substance which acts as an ozone-carrier, or Ozonträger, to use Schönbein's expression, a substance which transfers ozone from hydrogen-peroxide, and similar bodies. This is shown by the fact that, if the guaiacum is not blued at all, or only slightly, the blue color becomes very marked when a drop of ethereal solution of hydrogen-peroxide is added. From these observations the author infers—1. That the oxygen inhaled by living plants, and even by pulled fruits, for a time is ozonized, probably by entering into loose combination, as is the case with oxygen in the blood of animals; and, 2. That it is probable that the ozone-transferring substance existing in almost every fresh vegetable structure is that with which it is loosely combined, as the oxygen in the blood is with the hæmoglobin of the red corpuscles. This element in plants is gradually destroyed as decay comes on, and ceases to perform its ozone-transferring function when the fruit, etc., containing it is cooked. It is not chlorophyl, as is shown by its situation, and it seems to be intimately associated with the vascular tissue. From analogy with the animal substances, hæmoglobin, fibrin, myosin, etc., which have a similar action, it may be presumed to be proteinaceous, though the author is unable more exactly to indicate its chemical and other characters.

Growth of Mining Engineering In the United States.—Thirty years ago the profession of the mining engineer was almost unknown in the United States; to-day the American Institute of Mining Engineers numbers over 700 members. The state of things which existed thirty years ago. will be understood from the following passage, which we take from Mr. E. B. Coxe's presidential address to the members of the Institute at its last meeting: "Of the few we then had worthy of the name of 'mining engineer,' some studied in the Continental academies, and others were graduates in the school of practical experience, and had learned their profession in mines and smelting-works. Their work consisted principally in making surveys and maps of mines and mining properties, geological reports, and analyses of ores; but the mining engineer, whom we often meet with now, who has studied chemistry, physics, mineralogy, geology, mechanics, and drawing; who is more or less familiar with machinery and its construction, and with the practical