来自《耶鲁大学开放课程：1600年后西方社会的流行病 第14集 第14集》
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He left a batch of bacteria untouched for a week or so他将一组细菌无干扰放置一星期左右 -
while he went on vacation during the hot summer months.在此期间他去享受了他的盛夏假期 -
On returning, he found initially,to his frustration,回来时 一开始他很郁闷地发现 -
that the culture no longer produced the disease当他试图用培养体感染其他鸡的时候 -
when he attempted to infect other chickens.这些培养体不再起作用了 -
So, he got a fresh batch of bacterium,于是他又新取了一组新鲜的细菌 -
and injected the same chickens with it,给同一群鸡 -
as well as a lot of new chickens,以及许多新的鸡注射了 -
and made a surprising discovery.接着有了惊人的发现 -
That the original chickens, injected with the old vaccine,原来的那些鸡 注射了老疫苗以后 -
remained healthy--in our terms, they were immune--一直保持健康 也就是说 有免疫力 -
while the new and previously untreated chickens新的没有受到老疫苗注射的鸡