call of nature

Salman Rushdieの "Midnight's Children" を読んでいます。

On February 10th (when Yahyu, Bhutto and Mujib were refusing to engage in high-level talks), the buddha felt the call of nature. A somewhat concerned Shaheed and a gleeful Farooq loitered by the latrines; while Ayooba, who had used jump-leads to attach the metal footplates of the urinals to the battery of a jeep, stood out of sight behind the latrine hut, beside the jeep, whose motor was running.

"call of nature" で大昔に読んだ、たしか東京オリンピックの数年前で当時ベストセラーになった　「英語に強くなる本」（岩田一男著）に出ていた表現　"nature calls me" を思い出しました。その他の表現は何も覚えていませんが。
英英辞書にこの表現の説明があるか見てみました。
・Oxford English Dictionary: call of nature: Used euphemistically to refer to a need to urinate or defecate.: I did a quick escape at the end to answer a pressing call of nature.

・Collins Dictionary: Some people talk about a call of nature when referring politely to the need to go to the toilet.: I'm afraid I have to answer a call of nature.

生理現象は自然の摂理なのです。