American journal of physiology . e to get this phenomenon exhibited in agraduated manner. That is, with a certain strength of stimulusone obtains no change in blood pressure from stimulation ofthe left splanchnic and a slight increase from stimulation of theright; then by shghtly increasing the strength of the stimulusa rise in pressure is obtained from stimulation of each nerve,» Sch.\efer: Textbook of physiology, 1900, ii, p. i35- Vasomotor Phenomena in the Turtle 245 but the rise is greater from stimulation of the right. The greatervasomotor effectiveness of the right splanchnic has been ob
American journal of physiology . e to get this phenomenon exhibited in agraduated manner. That is, with a certain strength of stimulusone obtains no change in blood pressure from stimulation ofthe left splanchnic and a slight increase from stimulation of theright; then by shghtly increasing the strength of the stimulusa rise in pressure is obtained from stimulation of each nerve,» Sch.\efer: Textbook of physiology, 1900, ii, p. i35- Vasomotor Phenomena in the Turtle 245 but the rise is greater from stimulation of the right. The greatervasomotor effectiveness of the right splanchnic has been ob-served by Burton-Opitz ^ for the dog. It has long been recog-nized also that the right vagus in the turtle has a greater effectupon the heart than does the left. The fundamental characterof the latter problem has recently been shown in the interest-ing observations of Garrey ^ in which he found that the rightveins normally initiate the heart beat and that the vagi showa preponderant homolateral effect especially upon the basal. Figure 3. Showing the effect of a stimulus of equal intensity applied alternately tohomologous fibres of the left and right posterior splanchnic groups. Signal line isthe abscissa. Time line in seconds. veins. There is, however, no suggestion in his work that couldpossibly be extended to include the phenomenon of vasomotordifference as here shown. Results from stimulation of the anterior splanchnic group.— Stimulation of this group of fibres produces a small rise inblood pressure. The effects, however, as compared with thosefrom the posterior splanchnic group, are less sure and the amountof rise in pressure is never as great from a stimulus of equalintensity. This result probaby means a smaller number ofvasomotor fibres contained in the anterior tract. Langley andOrbeH ^ observed in the frog a less vasoconstrictor effect fromstimulation of the second spinal nerve than from the third andfourth. If we may homologize the two cases it would appear that 1
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