Guinea pigs were acupunctured at "ZuSanli" (ST 36) with one direction twirling manipulationuntil an objective sensantion was felt by operator's hand. Frozen sections and scanning electromi-croscopic specimens were made from the whole guinea leg acupunctured and were observed under lightmicroscope and scanning electromicroscope respectively. In all specimens

a puncturing pore and differ-ent transformation of surrounding tissue were seen clearly. In hypodermis the connective tissue fiberscircling the puncturing pore appeared as whirly form. In muscle layer

the connective tissue fibers ofendomysium circled the pore and the relative muscle fiber were twisted and dislocated. Adjacent vesselsand nerves were' dislocated and transformed. It is infered that various needling sensative tissues andstructures were simultaneously stimulated by twirling needle force

with connective tissue being as me-diator

which is likely of the biological basis of needling sensation and ist complexity.