Abstract: Abstract: The length and diameter of underfur and guard hair of Wistar-Imamachi rat population of 2 to 16 week-old were measured respectively． The 4 measurement indexes increase rapidly form 2 to 3 week-old and increase slowly from 3 to 4 week-old，the length and diameter of underfur and the length of guard hair increase slow remarkably after 5 week-old，but the diameter of guard hair increases rapidly again form 6 to 7 week-old， the growth rate slows down after 7 week-old and lasts to the old age．

Key words: Wistar-Imamachi rat, hair, week-old

摘要： 摘要: 对Wistar-Imamichi 大鼠封闭群2—16 周龄个体绒毛长度、绒毛直径、针毛长度和针毛直径分别进行测定。 4 项测量指标从第2 周龄到第3 周龄皆表现出一个快速增长现象，3—4 周龄生长放缓，5周龄后绒毛长度和直径、 针毛长度的数值增加甚微，但针毛直径由6—7 周龄再出现一次快速增长现象，之后又趋于平缓，这种现象一直持 续到老龄段。

关键词: Wistar-Imamichi 大鼠, 被毛, 周龄