【英语时差8,16】肘部和眼球的愈合

Healing Elbows And Eyeballs A scratch to the surface of your eye heals quite rapidly, often in a matter of minutes. But a surface scratch on your elbow takes days rather than minutes to heal. The reason for these different rates of healing is directly linked to the kinds of cells that exist on the outer-most layers of your skin and your eyeball. When your elbow or your eyeball is scratched, a layer of cells is actually scraped away from the surface. The healing of a scratch happens when new cells take the place of the ones lost to the minor¹ injury. When the outer layer of cells on an eyeball is scratched, cellular² replacement³ happens quickly because the surface of an eyeball consists of living cells. These living cells have the ability to rearrange themselves and migrate to where the cells are missing. The outer layers of skin, however, consist of non-living cells, sometimes layered three or four cells deep. These dead cells create a surface that protects the underlying⁴, more tender, living cells. Because they are dead, the cells that make up the outer layer of your skin can’t move like the living cells of an eyeball. In order for new skin cells to replace old ones–in other words, in order for healing to occur–live cells, several layers below the surface, must work their way up to the outer-most layer of the skin. When compared to the quick healing that the surface cells of an eyeball can accomplish, the healing of an elbow, which must begin several cell layers below the surface, can take a long time. 

1 minor   

adj.较小(少)的，较次要的；n.辅修学科；vi.辅修

参考例句：

• The young actor was given a minor part in the new play.年轻的男演员在这出新戏里被分派担任一个小角色。
• I gave him a minor share of my wealth.我把小部分财产给了他。

2 cellular   

adj.移动的；细胞的，由细胞组成的

参考例句：

• She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
• Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。

3 replacement   

n.取代，替换，交换；替代品，代用品

参考例句：

• We are hard put to find a replacement for our assistant.我们很难找到一个人来代替我们的助手。
• They put all the students through the replacement examination.他们让所有的学生参加分班考试。

4 underlying   

adj.在下面的，含蓄的，潜在的

参考例句：

• The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
• This word has its underlying meaning.这个单词有它潜在的含义。