研究人员发现了大约1000个种群，而且从个体到个体间分布一致；

The researchers found about 1000 species total, which were fairly consistent from person to person;

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研究人员发现了大约1000个种群，而且从个体到个体间分布一致；原来人们的鼻子里、背上都住的房客都大同小异。

The researchers found about 1000 species total, which were fairly consistent from person to person; it turns out we all have similar tenants in our noses and on our backs.

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The other problem is that as it was passed from me to another individual, to another individual, then the vaccine could change in some ways that were hard to predict because what accumulates in the lesion in my arm is different in some way than what accumulates in the lesion on a cow.

另外一个问题是当疫苗从我这传到另一人,到另一个个体,疫苗可能会发生某些改变,这种改变很难预测,因为胳膊上积累的病变,与牛身上积累的病变是不太一样的

耶鲁公开课 - 生物医学工程探索课程节选