1. It has long been known that the level of serum iron in animals falls during infection. 人们早就知道，在感染期间，动物的血清铁水平会下降。
2. One family of completely harmless snakes, the kingsnake, has also evolved serum that neutralizes rattlesnake venom. 一种完全无毒的蛇家族，王蛇，也进化出了能中和响尾蛇毒液的血清。
3. The virus was first identified in the State Serum Institute in Copenhagen, Denmark, in 1958 during an investigation into a pox-like disease among monkeys. 1958年，在对一种猴子中出现的痘类疾病的调查中，丹麦哥本哈根的国家血清研究所首次发现了这种病毒。
4. Colds mutate even while they're infecting you, and new strains pop up so often that by the time drug-makers create a vaccine against one variation, the serum is already out of date. 即使在感染你的时候，感冒病毒也会发生变异，而且新的病毒毒株经常出现，以至于当制药商研制出针对其中一种变异的疫苗时，血清已经过时了。
5. The serum glycocholic acid was yet higher than normal. 血清甘胆酸仍高于正常水平。
