高级医学英语阅读与写作Chapter two
2012-06-02 22:49:01   来源：37度医学网   作者：  评论：0 点击：

they have a ‘waist’. Those which have a waist are known as petiolata, and those which do not are called sessileventres.
 
In the first sentence the writer tells us his criterion for classifying, and in the second he names the classes. The paragraph is organized by division.
What is the criterion of classification in the following paragraph?
 
Energy sources may initially be divided into two kinds: non-renewable (i.e. finite) and renewable.The former group includes coal, oil, gas and, in the long run, nuclear; the latter hydropower, solar power and wind power. The energy from all these sources ultimately derives from the sun. There is a further source – geothermal – which depends on the earth’s own heat. In practice this may be classed as non-renewable as it is exploitable in only a few places and even there it is limited.
                            ―   Alex Adkins and Ian Mckean, “Text to Note”
 

                                           Energy sources

                                          ↙           ↘
                 Non-renewable                                    Renewable
        ↙  ↙ ↘   ↘                ↙     ↓      ↘
Coal  Oil  Gas  Nuclear     Hydropower  Solar power  Wind power
 
Parallelismis vital to a good classification. As shown above, we can classify energy sources into two categories: non-renewable and renewable. The criterion is whether an energy source can be renewed or not. If we classified energy sources into non-renewable, nuclear, oil, and hydropower, we would violate parallelism, for non-renewable energy source should be regarded as a general category, while nuclear and oil are subcategories of non-renewable energy source; hydropower is a subcategory of renewable category. Can you figure out the general categories of musical instruments and their respective subcategories in the following paragraph?
 
                                                 Music Instruments
 

 
Topic sentence
 
 
       Class 1
 
 
There are many different kinds of musical instruments. They are divided into three main classes according to the way that they are played. For example, some instruments are played by blowing air into them. These are called wind instruments. In some of these the air is made to vibrate. Inside a wooden tube, and these are said to be of the woodwind 
 
 
 
 
      
 
Class 2
      
 
 
Class 3
 
 
 
 
 
 
 
family. Examples of woodwind instruments are the clarinet and the bassoon. Other instruments are made of brass; the trumpet and the horn, for example. There are also various other wind instruments such as the mouth-organ and the bagpipes. Some instruments are played by banging or striking them. One obvious example is the drum, of which there are various kinds. Instruments like this are called percussion instruments. The last big group of musical instruments are the ones which have strings. There are two main kinds of stringed instrument: those in which the music is made by plucking the strings, and those where the player draws a bow across the strings. Examples of the former are the harp and the guitar. Examples of the latter are the violin and the cello.
  ―Michael J. Wallace

 
                                                                                      Clarinet
                                                           Woodwind       Bassoon
                             
                                                 Wind            Brass                 Trumpet
                                                                                           Horn
                                                      Mouth-organ
                                                                
                                                                Bagpipe
Musical instruments          Percussion ―Drum
                                                       
                                                                Plucking            Harp
                                                                                           Guitar
                                          Stringed
                                                                                           Violin
                                                                Drawing            Cello
                                                       
From the above sample paragraphs of division, it can be seen that the topic of the paragraph (e.g. musical instruments) is usually classified first into several categories. Then the different categories are defined or illustrated one by one; some, sub-classified.
 
Structure and Vocabulary Aid
 
Grouping:
constitute/form/make up/compose/ comprise
fall into/within
 
Division:
criterion/criteria; basis/bases; features; characteristics
 
        class                                             classes
        categorise                                      categories
sb.   group            sth. into two        groups
        divide                                            types
        put                                                 kinds
                                                               divisions
                                                              
 
        sub-class                                          sub-classes
sb.   sub-categorise     sth. into two      sub-categories
.      sub-group                                      sub-groups
               sub-divide                                       sub-divisions
                                                                       
                                           according to …
sth. may be classified        on the basis of …
                                           depending (up)on …
 
Note the possible sequence:
… may be divided …, … may be sub-divided …, … may be further sub-divided …