The aim of this paper is to give a textual genetic analysis of the 1936-1937 correspondence between the linguist Lucien Tesnière and the physician and grammarian Édouard Pichon. In 1935, Tesnière wrote a review of the third volume of Damourette and Pichon’s Essai de grammaire de la langue française. The draft of this review is highly interesting since it reveals that Tesnière takes a very different stance than that expressed in the published version of the review. This is what I show by comparing three versions of the review: the draft, the typescript version kept in Tesnière’s archives, and lastly the exchange with Pichon about the review. It appears that Tesnière defended clinical medicine as a paragon of scientific rigor, bemoaning the absence of such rigor in linguistics, and criticizing (quite bluntly in his draft) the attitude of his colleagues in linguistics. He then complimented Pichon for his methods, whereas Pichon refused to reduce his work to that of a medical practitioner. The debate is epistemological as well as a precious historical documentation, showing how these two disciplinary fields constituted themselves in relationship to each other in the first half of the 20th century.