THE WAX PLUG OF THE MYSTICETI 299 



are less differentiated, and the granular substance is augmented ; a great amount of keratinized squamous 

 epithelium appears between the columns of tissue as well as at their distal extremities. 



From the above description it may be concluded that the lumen of the meatus lies on the central axis 

 of the wax plug, but is completely occluded by the stratum corneum of the epidermis of the meatus. 

 The wax plug is, therefore, not merely an amorphous secretion but an intrinsic part of the meatus. 

 The stratum granulosum of the external meatus and the zona germinativa, which is highly vascular and 

 subject to rapid decomposition after the death of the animal, are presumably to be looked for on the 

 outer surface of the plug. 



A biochemical analysis of a fragment of the wax plug showed that it contained only 42-5 % total 

 lipoid, approximately half the quantity obtained from human ear wax, which contained 88%. The 

 analysis of the lipoids from whale and human ear wax is given below for comparison. The cholesterol 

 and squalene are included in the figures for total unsaponifiable matter. The comparatively large 

 amount of cholesterol is particularly noteworthy, since the figure given above is likely to be much 

 lower than the amount actually present in the wax plug of the living animal. The alcohol in which 

 Lillie's specimens were preserved contained a great number of large triclinic crystals of this substance 

 and the specimens themselves, when removed and partly dried, displayed a glistening surface-covering 

 of small crystals. 



DISCUSSION 



The above description of the histological and biochemical nature of the wax plug of the Mysticeti 

 shows that it is composed largely of solids with a maximum of 14% soft fatty acids and thus resembles 

 only very slightly and is not homologous with the ear wax of the human subject in which the propor- 

 tion of fatty acid may be five times as great. The keratinized squamae of epithelium are so closely 

 compacted that the structure can be said to be of a horny rather than waxy consistency, and it would 

 appear that the concentric layers of tissue are more or less continuous from the blind end of the external 

 meatus to the tympanic annulus. Although macroscopically the core of the plug appears to consist of 

 transverse laminations, the microscopic arrangement of the keratin is in the form of columns of tissue in 

 which the squamae of epithelium are predominantly parallel with the long axis of the plug. The matrix, 

 in which the squamae of keratin are embedded, is composed almost entirely of crystalline cholesterol 

 which is known to be able to absorb a considerable amount of water without going into solution, 

 and is well known for the formation of stony concretions in other parts of the body, e.g. gall stones. 



In view of the great amount of solid material present, it is not surprising that the wax plug is a good 

 conductor of sound, especially of high-frequency vibrations. During their experiments on the trans- 

 mission of sound through various organic tissues, Fraser and Purves, found that vibrations conducted 

 along an axis parallel with the direction of longitudinal fibres suffered much less attenuation than those 

 transmitted across the fibres, even though the difference between the acoustic resistances of the fibres 

 and their interstitial substances was very small. This phenomenon was well demonstrated in the case of 

 red muscle, the external meatus, the wax plug and wood, the latter two substances being broadly 

 similar in structure. 



