问题描述：
有高手能解释一下这句话里一个小弟看不懂的地方吗?
General George Washington ordered that his men be vaccinated against smallpox.
Their allegiance to him can be measured by the fact that they obeyed,for Washington's doctors used the actual smallpox virus,not the safer vaccination that Edward Jenner would introduce in 1798.
General George Washington ordered that his men be vaccinated against smallpox.
Their allegiance to him can be measured by the fact that they obeyed,for Washington's doctors used the actual smallpox virus,not the safer vaccination that Edward Jenner would introduce in 1798.
问题解答：
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