The study focuses on some points of the poetics used by Lucretius in the De rerum natura to express the living. The didactic mission claimed by the poet indeed requires the elaboration of a language of a vivid expressiveness and a flawless clarity to transmit the Epicurean doctrine. This is a difficult task when it comes to the birth of the living, which is conceived from inanimate atoms. We examine here the place held by the physiological paradigm through two recurrent motifs on this subject, birth and fluidity. Lucretius proves to be a virtuoso, knowing how to combine all sorts of mechanisms of language and poetic music in order to mobilize the mind of his reader. Building his poetics, he never dissociates his work from the fundamental principles of the doctrine he transmits: such as the concilium and the clinamen. We discover a re-evaluation of the didactic word, where the literary memory constitutes more than an intertext but becomes the material to be recomposed, even inflected, for the benefit of the dogma expounded and in close coherence with it.