American journal of physiology . ed, for convenience of treatment,into three groups. Each group is designed to show in a different waythe persistence of vagus effects upon the auricle after the productionof complete sino-auricular block. The general method employed hasbeen to take tracings by levers attached to the great veins or sinusand to one of the auricular appendices after the heart has been freedfrom its attachments except at the base. The coronary nerve and veinare cut in all of the experiments, and a clamp, which is of the modifiedGaskell type, is applied, and compression produced suf
American journal of physiology . ed, for convenience of treatment,into three groups. Each group is designed to show in a different waythe persistence of vagus effects upon the auricle after the productionof complete sino-auricular block. The general method employed hasbeen to take tracings by levers attached to the great veins or sinusand to one of the auricular appendices after the heart has been freedfrom its attachments except at the base. The coronary nerve and veinare cut in all of the experiments, and a clamp, which is of the modifiedGaskell type, is applied, and compression produced sufficient to com- 249 250 Waller E. Carrey. pletely block all impulses passing from the sinus to the auricle. Fromthis point on the procedure varies in the three types of experimentswhich have been performed. I. After clamping, time is permitted for the auricles to initiate arhythm of their own. This may be facihtated by the appHcation of afew drops of m/S sodium chloride solution. When the auricular ViAA/LAyiAAAywAr|yiA/l/,yuTj^^. rhythm is fully developed, a minimal strength faradization is appliedto one of the vagus nerves, whereupon we see a t^pical vagus effect uponauricular contractions; viz., a gradual weakening in the strength of thecontraction followed, subsequent to the cessation of vagus stimulation,by gradual return of normal strength of contraction of the strong stimulation of the vagus nerve is resorted to, the decrease inthe strength of contraction of the auricles is quite sudden, and thesecontractions may cease entirely, the whole heart becoming results are graphically illustrated in Figs, i and 2. In Fig. I the clamp had been gradually tightened at the sino-auricular groove, producing all the intermediate stages up to completeblock. The tracings are taken from the sinus venosus and right auricle,which are beating in independent rhythms, as is shown by the study ofthe time relations indicated by the lines i, 2, 3, 4, 5, corresponding to
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