Lysozyme is a substance in tears, described by Fleming1 in 1922, which has a strong lytic action on certain organisms. It is also found in nasal mucus and in saliva, but it is especially abundant in egg white, tears and leukocytes. Lysozyme is characteristically a ferment : It is water soluble, will not pass through a semipermeable membrane and is destroyed by boiling water but not by light or drying. Its optimum action in a neutral medium is attained at 56 to 60 C. Lysozyme even in high dilutions destroys many saprophytes of the air and is, therefore, thought to have the function in the eye of keeping the conjunctival sac free from atmospheric organisms. The significance of lysozyme for pathogenic organisms is debatable,2 but Ridley3 maintained that it does prevent the growth of some organisms. For further details on the lytic principle of tears, the reader is