Hollow Casts of Lungs for Experimental Purposes

Abstract

SEVERAL techniques have been described for producing solid casts of human and animal respiratory tracts in wax¹, Wood's metal² and ‘Vinylite’³. Made with care, these casts keep the fine detail of the airways extending as far as the respiratory bronchioles. But because the casts are “negatives”, in that they represent the airspaces rather than the airway walls, their use has been limited to demonstrations of anatomical features and pathological changes⁴. Hollow positive casts for use in airflow studies have been made from these negatives by conventional casting techniques; some made in resin^5,6 have contained the airways from the trachea as far as the segmental bronchi. This article describes a technique for producing hollow casts which keep the fine detail obtainable in the solid models; a hollow cast of a pig's lung is shown in Fig. 1. Preservation of detail of the respiratory bronchioles greatly increases the value of such casts for the study of airflow and of particle deposition. The casts are made by spraying a negative wax cast with colloidal silver and electroplating onto the conducting layer a firm structure from which the wax is then removed.