138 PRACTICAL PHYSIOLOGY 



artificial respiration established at once; a tube is put into trachea 

 and connected with a small hand bellows; the ear is shaven and 

 fixed by threads to a loop of stout wire. This wire is clamped in 

 front of the lantern, so that the blood vessels in the ear can be 

 plainly seen. The cervical sympathetic is exposed in the neck, 

 where it lies behind the carotid artery, and is traced up to the 

 superior cervical sympathetic ganglion. The thread is tied round 

 the nerve, and the latter is cut. Observe that at this moment the 

 blood vessels in the ear dilate and the ear becomes warmer. The 

 palpebral fissure at the same time becomes narrowed. The change 

 will be much more marked had the ear of the rabbit been previously 

 exposed to cold. The cervical sympathetic exercises a tonic action. 

 On exciting the peripheral end of the nerve with the faradic current, 

 the vessels in the ear will be seen to constrict, and this will take 

 place to such a degree that all the smaller vessels will disappear 

 from view." The ear will at the same time become several degrees 

 cooler. Note that the latent time is considerable between the 

 excitation and the effect. Note that the pupil also dilates, the 

 nictitating membrane retracts, and the palpebral tissue is widened. 

 The eyeball at the same time projects forwards. The pupillo dilator 

 fibres arise from the first three thoracic anterior roots, the vaso- 

 constrictor fibres from the second to the fifth, and even to the 

 seventh, in the rabbit. If the superior cervical sympathetic ganglion 

 be painted with nicotine, excitation of the preganglionic fibres will 

 no longer have any effect on the ear, while excitation of the post 

 ganglionic fibres will still be effectual. The sympathetic fibres to 

 the head have their cell-stations in this ganglion. 



The Circulation Time of the lesser Circulation. The carotid artery 

 is exposed. A piece of thin rubber membrane is placed beneath it. 

 Between the membrane and the artery a piece of white paper is 

 inserted. The artery is illuminated by a strong light. 



The external jugular vein is exposed on the other side of the 

 neck, a clip is placed on the vein below and it is tied above, and 

 into its central end a cannula is inserted. The vein cannula is 

 connected with a glass syringe containing a 0*2 per cent, solution 

 of methylene blue in physiological saline at body temperature. Put 

 a screw clip on the piston so that one-third of the contents shall 

 be ejected. The clip is removed from the vein and at a signal 

 from the assistant who times the experiment the syringe is pressed. 

 The stop-watch is stopped by the assistant the moment the blue 

 appears in the artery. The observation is repeated several times 

 with the same amount of injection. 



