American journal of physiology . ile strong stimuli augment both the rate andintensity of the impulses. The effects may persist for two to ten min-utes after the cessation of the stimulation. The fact that the afferentphrenic fibres are strongly stimulated by the mere sectioning of thephrenic seems to show that this is a factor in the immediate crossingof the respiratory impulses in the Porter experiment. But, as the Bulbar Respiratory Impulses in the Spinal Cord. 6i iii i i iii ii I m I 11 i i>if-iutiit»i Figure 3. — Four fifths the original size. Cat. Tracing on stimulation of the central
American journal of physiology . ile strong stimuli augment both the rate andintensity of the impulses. The effects may persist for two to ten min-utes after the cessation of the stimulation. The fact that the afferentphrenic fibres are strongly stimulated by the mere sectioning of thephrenic seems to show that this is a factor in the immediate crossingof the respiratory impulses in the Porter experiment. But, as the Bulbar Respiratory Impulses in the Spinal Cord. 6i iii i i iii ii I m I 11 i i>if-iutiit»i Figure 3. — Four fifths the original size. Cat. Tracing on stimulation of the centralend of the left phrenic nerve, right phrenic nerve intact. Increased activity of therespiratory centre. mmmmmmmMkmiHM iiliiiii« f/iitiMMiw/uwvj/wHmmu ,V««««*««M«M««/«VW^*™*^*^ FiGLTvE 4. — Two fifths the original size. Cat. Tracings of the carotid pressure andthe respiratory movements. Both phrenic nerves sectioned. Stimulation of cen-tral end of left phrenic nerve. Increased activity of the respiratory Figure 5. — Eight ninths the original size. Cat. Respiratory tracing via the trachealcannula. X — light traction on central end of the left phrenic nerve. Increasedactivity of the respiratory centre. 62 /. Deason and L. G. Robb. crossing persists, according to Porters observations, after such stim-ulation of the afferent fibres due to the section of the nerve has pre-sumably ceased, other factors must also be involved, possibly anincreased excitabihty in the phrenic nuclei, due to injury currentsand products of degeneration. Stimulation of the sciatic nerve induces crossing of the respiratoryimpulses and an equal contraction of each lateral half of the diaphragm,which may continue for ten minutes after the cessation of the stimulation. One typical experiment may be cited for illustration. Experiment 26.— Kitten. Ether. Cervical cord exposed. Abdomen opened. Diaphragm sectioned from xiphoid process to
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