主句：We chiefly think of texts as graphic representations .其中：think ...of..是固定搭配,辨认出来,of spoken language or numbers ,of .做定语修饰representation,
from which the living body is extracted.,是定语从句部分.from 是搭配着的介词,更好地理解,我把它改成陈述句：the living body is extended from language or numbers .在此,把 language or numbers 提前 ,把is extended from 搭配拆开,介词from 提前,这是定语从句的语法,显而易见,这是定语从句.
which指代 the living body .is extended from 的东西,也就是这里的language or numbers .
不要犹豫,is extracted from的主语就是the living body,从句一般不到装,所以顺着来.（除了一些固定的搭配要倒装,例如nor之类的,那就显而易见了）