这是惯用法问题。商务印书馆2014年9月第1版《英语词语用法详解词典》指出：

    by 与 catch，hold，seize，take 等动词连用时，习惯用“catch [take, etc.] sb. + by the +具体部位”结构。例如：He seized her by the hair.他抓住她的头发。/ I caught the thief by the arm.我抓住贼的胳膊。/ She took me by the hand.她抓住我的手。

    不可说：He seized her by her hair./ I caught the thief by his arm./ She took me by my hand.