Physiology : A manual for students and practioners / by Theodore C. Guenther and Augustus E. Guenther.

  • Guenther, Theodore C. (Theodore Charles)
Date:
1903
Catalogue details

Licence: Public Domain Mark

Credit: Physiology : A manual for students and practioners / by Theodore C. Guenther and Augustus E. Guenther. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    eHW't is not iinnuMlinte, l)ut follows u latent periofi which oxteuds oviT a lu'at or (wo. The inlilhifion inanifi'sts itself at first hy a leii;.ftheiiiii<; of the duralioii of (he diaslole without any ehanjre in the systole. A stronj,aM-sdniulation lengthens the .systole also, and may stop the heat of the heart altogether. Inhibition is further xlioH'tt hy a /('xsniinf/ oi' the force of the (•otilraction ; by an increase of ]>reKKurt' in the lieort during diastole; \)\ on increase in the amount of residual blood; hy a decrease in the injtiit and oiifjtitt of the ventricle, and hy diminished ventricular tonus. It inav further he said that during vagus excitation the j)roj)agati(«i of the cardiac excitation is more ditiicnlt. A demarcation current tlerived from a jMjrtion of the auricle is increased by var/us excita- tion, although the auricle shows no visible change of form. The heart cannot be continuously inhibited by prolonged stimulation. Fig. 14. 'y.vA\z\\\z%%mmwMmmwmm/immm'aiivMMmmMv^ Effect produced by stimulatidU f)f ]< ripliernl cml nf tlu' iKcvliintiriK iutvl' of the heart. The licart beats mure quickly. Stiimilatiuii begun at >' ^LaudoJs). It e-scajies from the influence of the vagus and resumes its former rhythm with perhaps increased force. Immediate stitnulafiini of the second r«7».*i after the heart has escaped from the influence of the first is without effect, making it probable that both uerve.< act upon the same mechanism in the heart. Stimulation of the siimj»athetic or augmevtor fibres causes an in- crea.se in the rate of the heart-beat from 7 to 70 per cent., the amount of increase de]HMiding upon the heart's rate before stimu- lation. A lonff excitation jiroduces no (jreater acceleration than a sfitirt one. The force of the beat, the pjilse-ndume, and the sj)erd i)f the e.rcitation-u'ave are all increased. The latent ])eriod is usually a long one, extending from two to ten seconds. The accel- eration may continue for .several minutes after the excitation has ceasetl. It ha.s been found that pressure brought to bear U|M>n the human heart where a defect in the chest-wall makes it acces>i-