首先，我们把句中的主干和修饰成分都标注出来，可以发现这个长难句包含1个定语从句，6个介词短语： The change met the technical requirements (of the new age) (by engaging a large professional element) and prevented the decline (inefficiency) [that so commonly spoiled the fortunes（offamilyfirms) (inthesecondandthirdgeneration)(aftertheenergeticfounders.)]
下面我把这6个介词短语和其修饰的成分一一摘出来看一下： technical requirements (of the new age) 新时代的技术要求； met the technical requirements …. (by engaging a large professional element)：通过雇佣大量的专业人员来满足技术要求，这里by引导的短语来修饰整个动作； 所以(of the new age) (by engaging a large professional element) 这两个介词短语修饰的成分各自不同，of 短语修饰名词，by短语修饰动作，需要加以区分。
prevented the decline (in efficiency) (that引导的定语从句)，充当修饰成分的定语从句和被修饰的decline中间添加了一个in efficiency，像这种修饰成分和被修饰成分中间有介词短语阻隔的句子，我们也需要多加留意。而the decline (in efficiency) 介词短语修饰decline，in 表示“在 … 方面”，该短语理解为“效率下降”。
spoiled the fortunes (of family firms) (in the second and third generation) (after the energetic founders.)这里三个介词短语先后出现，我们也需要注意各自修饰的成分分别是什么。 the fortunes (offamilyfirms) 家族公司的财富 spoiled the fortunes offamilyfirms (inthesecondandthirdgeneration)，在第二代和第三代毁掉家族公司的财富，而不是毁掉第二代和第三代家族公司的财富。 inthesecondandthirdgeneration (aftertheenergeticfounders)，这里after引导的介词短语修饰the second and third generation：在精力充沛的创业者之后的第二代和第三代。
1. 介词短语作表语： Mr. Smith is still in bed. 史密斯先生还在睡觉。 He was already in his sixties. 他已经六十多岁了。 Dinner was at one o’clock. 一点钟开午饭。 We are out of food. 我们的食物吃完了。
2. 介词短语作状语： The children are playing by the river. 孩子们在河边玩。 They often talk in English after class. 他们经常在课后用英语交谈。 Let’s go out for a walk along the river. 咱们到江边散散步。
3. 介词短语作定语： The woman in the room is his wife. 房间里的那个女人是他的妻子。 China is a country with a long history. 中国是一个历史悠久的国家。
注意：介词短语作定语时必须置于被修饰名词之后，如： the people on the bus 公交车上的人 the girl in front of me 我前面的女孩 a woman in black 一个穿黑衣的妇女 a book with red cover 一本红色封皮的书
4. 介词短语作宾语补足语： We found her in tears. 我们发现她在哭泣。 The cold kept him in bed for three days. 这次感冒让他卧床三天。
当含有宾语补足语的句子变成被动语态后，原来的宾语补足语就变成了主语补足语。如： She was found in tears. 介词短语作主语补足语。
