The morphological structure of Jinlo (or Meridian)--a hypothesis of sympathetic sensitive lines along skin is studied. At first, sympathetic substance lines(SSL) are displayed by macro autoradiography with 125 I tyrosine tracer. The lines are continuous from head to feet, symmetric in the left and right and connect each other in the head and feet to form loops. When the upper back skin where the SSL passed is severed, the effect of acupuncture analgesia produced by stimulating acupoints in the hindlimb is blocked significantly. Moreover, the SSL are proved coming from the dense adrenergic nerve endings innervating arrector pili muscles observed by fluorescent microscopy. As a conclusion, the hair follicles and its arrector pili muscles along the SSL are the morphological structure of Jinlo and act as dynamic target organs for long distance transmission of messages. Secondly, the rats hair are sheared as 12～16 rings from head to leg. Acupuncture and injection of phenylephrine at back skin along SSL produce pilomotor lines from hip to cheek, which is identical with SSL. Finally, after shaving all rat hairs, the first wave of hair growth distributes along lines and loops, which is identical with SSL. Thus live animal model is moken for displaying the Jinlo lines along rat skin.
