In a consideration of the causation of the common cold the predisposing factors must be included in addition to the inciting agent or agents. However, these factors will not be well understood until more complete information pertaining to the physiology of the upper respiratory passages is available, although physiologic features such as ciliary action have already been thoroughly studied.1 In addition, various properties of nasal secretions, including activity of the lysozyme2 and viricidal action,3 have been examined and have been shown to represent physiologic activities related to the defense of the nose against infections caused by bacteria and viruses. Other factors, such as air currents4 and variations in the supply of blood,4 have received inadequate attention.
Fabricant5 has recently studied a physiologic property of the nasal mucosa, namely, its pH, which might affect both nonspecific and specific defense mechanisms of the nose. He approached the problem directly be making the