We applied electro-acupuncture to the subcutis of the point as if it weredone to Huantiao and/or Xin Ming for man on both sides of the intact andthe sympathetic surperior cervical ganglionectomy animals

and hence thepain thresholds elicited were greatly enhanced.During acupuncture analgesia

tissue specimens were taken from the points of subcutis surrounding the ne-edles

and then examined for their innervation of afferent receptor and nervefibers by means of catecholamine fluorescence and cholinesterase(ChE).They are mainly free nerve endings and ChE-positive nerves.After sympa-thetic ganglionectomy

they are still surviving.We think that in the subcutissurrounding needles

the free nerve endings may be the afferent receptor ofacupuncture and the thin unmyelinated nerve fibers(ChE-positive nerves)may be the peripheral path of conducting needling sensation.Needling ofacupuncture points(Xin Ming and Huantiao)had noticeable elevation of localskin tempereture.The terminal branch of ChE-positive nerve seemed to bethe innervation to the resistance vessels and the subcutis near it.This kindof morphological relation is axon reflex which might be one of the causesto elevate the local skin temperature of these points.