英语达人来讲解一个句子~...the teacher should be prepared to devote some

英语达人来讲解一个句子~
...the teacher should be prepared to devote some of the lesson time to this,and by his whole attitude to the subject should get the student to feel that here is a matter worthy of receiving his close attention.
对已第二分句里德那个"by"很是不解,谁来指教下啊~