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A TEXTBOOK OF PHYSIOLOGY 



of the face and limbs impeded. Hence the veins stand out " knotted " 

 in a straining man, and the pressure rises within them towards arterial 

 pressure. 



During a run the rhythmic movements help to pump the blood 

 through the muscles and back to the heart. The control of the blood- 

 supply to the limbs has been studied by the thermometric or plethys- 

 mographic method. The temperature in the upper limb is raised by 



.R'hind limb 



L'h ind limb 



Kidney 



Jejunum 



Fe-m.Art. 



Eocc Sciatic 



FIG. 128. To SHOW EFFECT OF EXCITATION OF THE SUPERFICIAL BRANCH OF CRURAL 

 NERVE ON THE ARTERIAL PRESSURE AND ON THE VOLUME OF THE SPLEEN, 

 JEJUNUM, KIDNEY, AND FEET. (Hallion and Frai^ois-Frank.) 



destruction of the first thoracic ganglion, by section of the brachial 

 plexus or mid-thoracic roots. In the hind-limb a rise of temperature 

 occurs after dividing the sciatic nerve. The vaso-motor fibres have 

 been traced to the lower thoracic roots. They pass down the sympa- 

 thetic chain in the lower lumbar region. On excitation of these vaso- 

 motor nerves, the greatest change of temperature is found in the feet. 

 This is so because the pad of an animal's foot is free from a furry coat, 



