「時間」是歷史學自別於其他學科之重要特色，凡制度的建立，通常需要時間的累積始能臻至完美之境界。ㄧ種目前看似完備的制度，也都要經歷時間的磨練與挑戰，才能達到理想的狀態，但人們總是關注眼前所見到的，往往忽略了它的形成過程。本文以漢代蘭臺令第二與第三之形成為例，剖析二令如何從漢初的詔書中，經過多次的分化與重整，歷時二百多年，最後在後漢中期才形成兩條漢令，此期間之演變，可謂複雜至極。
蘭臺令第二與第三出自於〈王杖詔書令〉，在王杖簡之前，世人並不知道蘭臺有令。昔日多以為蘭臺是兩漢的藏書所，但這兩條漢令卻與圖書管理無涉，因此有必要重新理解漢代蘭臺之角色，本文即基於此需要，嘗試解讀此二令之所以著于蘭臺的原因。

Time is the important characteristic that history differences from the other scholarships. To build up any system, needs a long time to reach a perfect state. A system that seems perfectly now, also needs time to steel itself and challenged, able to reach a perfect condition, but people always follow with interests about the things that put before their eyes. This thesis will give two examples to analyze the Han’s regulations were how from emperor’s orders turned into country’s laws and regulations. The Lan Tai’s 42nd and 43rd regulations were disunited and rallied many times during two hundreds period, finally formed two regulations in middle East-Han Dynasty. Their variations were very complicated.
The Lan Tai’s 42nd and 43rd regulations stemmed from Wong Jhang
Jhao Shu Ling, before Wong Jhang Jian, people did not know the Lan
Tai’s regulations. In former days, people thought that the Lan Tai was the place where collected the books, but the Lan Tai’s 42nd and 43rd regulations were irrelevant to books, so we have to study the Lan Tai again. Because of these reasons, this thesis tries to explain why the two regulations established in the Lan Tai.