This is a clear-cut treatise on cavities of the lungs, their classification, their origin, their treatment and their healing, together with many interesting observations by the author. The term "spéléologie" belongs to a branch of geology and refers to the study of fissures, caverns and gulfs that occur in the interior of the earth. The author designs to apply the term to caverns in the lungs. It is pointed out in the paper that it has been difficult to reconcile clinical observation with postmortem appearances, but, since the advent of the x-rays, the records on the film, being permanent and susceptible of interpretation by competent observers, serve to clarify the subject. Jaquerod divides cavities into three classes or degrees: The cavity of the first class, he says, is characterized radiologically by an annular shadow, relatively indistinct, of which the interior is not completely clear, and clinically by the absence of