Archives of Diagnosis Volume 7

Archives of Diagnosis Volume 7

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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. 1914 edition. Excerpt: ...we come to study the functions of the primitive cardiac tube in the lower vertebrates (as for example the frog, in which portions of the primitive tube still exist, as the sinus venosus, auricular canal and the aortic bulb), we find that all of its parts possess in a high degree the power of originating stimuli, but the posterior portion of the tube as represented by the sinus venosus is even more excitable than the other parts of the tube, hence normally the cardiac contractions start from the sinus. The capability of parts of the frog's heart, other than the sinus, to originate stimuli resulting in contraction, is demonstrated by the Stannius experiment. When a ligature is so applied as to separate the sinus venosus from the auricle, the sinus will continue to contract rhythmically, but the rest of the heart ceases to move; after a time, however, the auricle and ventricle again begin to beat, but at a rate slower than that of the sinus and quite independent of the sinus rhythm. If now a second ligature be applied between the auricle and the ventricle, the auricle will continue to beat and after a short pause the ventricle will begin to contract rhythmically at a rate slower than that of the auricle and independent both of the sinus and of the auricle. I There are several phenomena presented in this experiment which particularly attract our attention. I. The capacity of each chamber to initiate rhythmic contractions independent of the other parts of the heart. i II. The rate of the spontaneous rhythmic contractions is fastest for the sinus, intermediate for the auricle, slowest for the ventricle. III. In the intact heart before such ligatures are applied the rate of the rhythmic contractions of the whole organ is determined by the...show more

Product details

  • Paperback | 164 pages
  • 189 x 246 x 9mm | 304g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236778936
  • 9781236778932