The London Medical Record Volume 4

The London Medical Record Volume 4

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: ...of a millimetre, is examined under the microscope, by means of an object-glass, which is covered with a perforated plate one-fifth of a millimetre in thickness; of this the square of the fifth of a millimetre may be cut off by a micrometer, and the number of corpuscles readily counted. He next called attention to the mode of measuring, the time occupied by a reflex process, such as sneezing, etc., which processes are found to consist of three stages; first, the stage of reception of an impression; secondly, a stage corresponding to the changes in the brain; and thirdly, the process by which the effect is conveyed to the muscles which act. This measurement is usually represented graphically by marking the periods upon a revolving cylinder. The periods are marked by signals given through the means of a voltaic circuit, and an apparatus by means of which a variation in the circuit can be made so as to record a signal. The same act may record the time of a signal on the cylinder, and send an impression to a sensory nerve; the individual experimented upon may then make a signal as quickly as possible, and thus the time required for the three stages is recorded on the cylinder. The time occupied by these different stages may be analysed by varying the conditions of the individual--e.g., I. when he knows the time when the signal is to be given; 2. when he expects the signal but does not know the time; 3. when he does not expect the signal. The experiments were then performed, and the tracings handed round. In each of these experiments the time differed, being longest in the last and shortest in the first. The exact measure of the time occupied by each of these periods may be then compared with a physical standard. For this purpose, a tuning-fork...
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Product details

  • Paperback | 672 pages
  • 189 x 246 x 34mm | 1,179g
  • United States
  • English
  • black & white illustrations
  • 1236910265
  • 9781236910264