Is the buccal cavity of the frog a respiratory chamber? In a letter to NATURE, March 24, Mr. M. D. Hill accepts this conception of it, and yet the only evidence which can be offered in support of ...

Each pleura is a single membrane that folds back on itself to form two layers. The space between the membranes (called the pleural cavity or intrapleural space) is filled with a thin, lubricating ...