The sciatic nerves of rabbit were frozen with different temperatures(-20℃,-60℃, -- 100℃, -140℃ and 180℃).The morphology and function of the frozen nerves were examined with light microscopy (HE stain and histochemical thiocholism method), electron microscopy, and short latency sematesthelic evoked potentials(SSEP), sensory conduction velocity(SCV), electromyo-gram(EMG) at various time intervals after freezing. It was showed that there were no changes in morphology and function of nerves after being frozen at -20C. The nerve fibers showed signs of frozen degeneration and lost their conduction function at -60℃. However, the nerves could recover in this group. About one half of the nerve fibres frozen with -100℃ showed Wallerian degeneration, and the time of repair was delayed. But still the regeneration of nerves was complete. Necrosis of nerve fibers occurred immediately after freezing with -140℃ and-180℃. There were destruction of the basement membrane and proliferation of collagen fibers. The results explained the mechanism of cryoanalgesia clinically. We believe that the temperatures lower than -140℃ are optimal for cryoanalgesia.

Objective: Ban Fenghe recorded in the Quality Standard of Yao Medicine of Guangxi Zhuang Autonomous Region (Volume 1) is derived from the dried stems and leaves of Semiliquidambar cathayensis. It is usually confused with medicinal herbs from Pterospermum heterophyllum and Dendropanax dentiger. However, they are very different in chemical composition, and should not be used as the same drug. To ensure their safety and efficacy, a method based on macroscopic and microscopic characteristics was developed to distinguish them. Methods: A total of 14 batches of Ban Fenghe samples from three species were collected from different producing areas in China. The macroscopic characteristics were examined by observing external traits. The tissue structures of transverse sections of stems and leaves, the leaf epidermis, and the powder were observed microscopically. Results: The branchlets and leaf surfaces of S. cathayensis and P. heterophyllum were hairy, especially the lower leaf surfaces of P. heterophyllum were densely covered with hairs, but those of D. dentiger were hairless. The pericyclic fibers of S. cathayensis stems were intermittently distributed in a circular shape and accompanied by stone cells, whereas those of P. heterophyllum and D. dentiger were bundled without stone cells. So stone cells and hairs were present in S. cathayensis powder, stone cells were not found in P. heterophyllum and D. dentiger powder, and hairs were not present in D. dentiger powder. The distribution sites, sizes and types of secretory tissues of these three species were also different in transverse sections of stems and leaves. Stomata on the lower epidermis of S. cathayensis leaves were paracytic, whereas those of P. heterophyllum and D. dentiger were anomocytic. Conclusion: Ban Fenghe drugs derived from S. cathayensis could readily be distinguished from those of P. heterophyllum and D. dentiger by macroscopic and microscopic features.