Recherches sur les maladies chroniques. Vol. 1. Analyse médicinale du sang.

De Bordeu first conceived the idea of internal secretion by his hypothesis that every organ, tissue, and cell discharges into the blood products which influence other parts of the body. His work was published in a collective volume by three physicians from his family: Antoine de Bordeu, Théophile de Bordeu, and François de Bordeu. Théophile's Analyse médicinale du sang appeared as part six of the book (pp. 346-588). In the first edition he was not specifically credited as author. Digital facsimile from Google Books at this link.