Vibration applied to the human palm or sole skin induces the tonic finger or toe flexion reflex. This reflex occured merely in 30per cent of the subjects, however the toe flexion reflex was induced in almost all subjects by increase of voluntary flexion of the toe or upward rotation of the ancle joint. This reflex was used as an indicator of the effectiveness of acupuncture stimulation (AS). Electroacupuncture stimulation was mainly applied to the skin with the intensity of perception threshold. AS sites used were Ho-ku, Wai-kuan, etc As a rule, this reflex was inhibited strongly and the inhibitory effect continued for 30min or more. AS applied simultaneously to the acupuncture point and its neighboring area showed summation of the inhibitory effect on the reflex. There was no difference between the effects of AS applied to the same or neighboring dermatome. AS to periphery of limbs was effective but AS to the body was almost ineffective. These results suggest that there is no specificity of the acupuncture point and there are both segmental and nonsegmental mechanisms participate in this inhibitory of AS on vibration-induced flexion reflex.

The two-point fused sensory area (fused area) was calculated from two-point fused distance. The fused area was enlarged by acupuncture stimulation. This enlargement of the fused area by acupuncture was explained on the point of the central nervous mechanisms.
Applying the two points of touch and pressure stimuli to the skin, the threshold separation required for the two stimuli to be noticed as one rather than two points was determined. On the same region of the body, three longitudinally combined points and one transversally combined point were measured and the area which was surrounded by them was calculated.
The fused area was more enlarged through the touch stimuli than through the pressure ones. On the upper limbs, the shape of the fused area was like an oblong and the area was smaller at the peripheral part than the central part. Acupuncture stimulation enlarged the fused area. This was concerned that the lateral inhibition could not be worked in the tract by impulses which were generated by acupuncture.

It is said that the key to effective acupuncture is to perform appropriate stimulation of the best combinations of meridian points which directly or indirectly affect the disease.
In order to determine the difference in the efficacy between combinations of clinically important meridian points, this study examined the effect of two-point acupuncture stimulation on the exteroceptive vibration-induced finger flexion reflex (Eklund et al., 1978).
METHOD
Subjects were six healthy adults of both sexes between 20 and 35 years of age. Two-point combinations were made of IC₄ Hegu (standard point) with each of the following points: IC₆ Pianli, P₇ Lieque, C₃ Shaohai, TM₂₀ Baihui, VU₁₃ Feishu, VU₂₅ Dachangshu, G₃₆ Zusanli. Perception threshold electrical stimulation of each combination was performed at 45Hz for 5min. using subcutaneous needles. The finger flexion reflex was induced by a tapping vibrator applied to the palm and recorded through a pressure transducer.
RESULTS
1) The combination of adjacent points on the hand: Stimulation of Hegu together with Pianli, both of which are on the Large Intestine meridian, caused a strong inhibition of the reflex. The inhibition lasted about twice as long as that caused by stimulation of Hegu alone. However, neither Hegu and Lieque not Hegu and Shaohai stimulation caused prolongation of the inhibition.
2) The combination of the hand and the back: Neither Hegu and Feishu nor Hegu and Dachangshu stimulation caused any prolongation of the inhibition.
3) The combination of the hand and the leg: Hegu and Zusanli stimulation caused marked inhibition, which lasted about four times as long as that caused by Hegu-alone stimulation.
4) The combination of the hand and the head: Hegu and Baihui stimulation caused no or much less inhibition that caused by Hegu-alone stimulation.
5) Examination of difference among stimulating methods: Electrical stimulation through surface electrodes (A), Retained subcutaneous needles (B), Electrical stimulation between a subcutaneous needle and the indifferent electrode. (C), Electrical stimulation between subcutaneous needles (D). The intensity of the inhibition effect of these methods can be expressed as follows:
D>C>B>A
DISCUSSION and CONCLUSION
The reflex inhibition caused by the standard point stimulation was strengthened or weakened by simultaneous stimulation of an additional point. Based on our examination of the characteristics of the inhibition, it was thought that not only mutual interference of impulses at the spinal level but also humoral factors and some polysynaptic reflex mechanism in the higher center level participate in this effect.