Objective:To study the effects of paraffin embedding and section-staining on the contraction of rat spinal cord.Methods:After fixed by 4% paraformaldehyde through heart perfusion

the lumber intumescentia(L4～6) of rats were separated and weighed.Afterwards

their length and density were also measured

thus the volume can be calculated.Then the lumbar intumescentias were divided into 6 sections equally

and one section was randomly selected and embedded by paraffin

and serially sectioned(14 μm).According to the systematic random sampling principles

sections were sampled per 15 sections

and the first section was chosen from the first 15 sections randomly.These sections were stained by hematoxylin and eosin.The area and thickness of each section was measured by VIS stereological system.Thus

the volumes of spinal cord after embedding and section-staining can be calculated.Compared with their initial volumes after fixation

the contration coefficient could be calculated.Results:The volumes of the lumbar intumescentia after fixation

embedding and section-staining were(96.80±13.85) mm2

(60.19±19.15) mm2 and(42.97±16.02) mm2 respectively.And the contration coefficient after embedding and section-staining were 62.9%±20.5% and 44.8%±16.6% respectively.Conclusion:The spinal cord contracts obviously after paraffin embedding and section-staining.These changes should not be ignored when morphometric studies are done.