THE WAX PLUG OF THE MYSTICETI 297 



more in length, depending upon the size of the animal. The specimen under examination measured 

 60 cm. The attenuated distal extremity of the plug is so flattened dorso-ventrally that it is extremely 

 fragile and delicate, and there is little doubt that it had become detached from Lillie's and Turner's 

 specimens before these were described. 



The proximal portion of the wax plug takes the form of an elongated, slightly curved and laterally 

 compressed cone, the base of which is deeply concave and drawn out peripherally into a delicate skirt, 

 one side of the latter being longer and more attenuated than the other. One aspect of the external 

 surface is sharply convex and another slightly concave and presenting a fluted appearance. In short, 

 the wax plug is an internal cast of the corium of the external auditory meatus. In addition to the above 

 features the whole surface of the plug is marked by a series of minute grooves running parallel with its 

 long axis which are the external manifestation of the complicated pleating of its internal structure. 

 The concave surface of the base, which is moulded to the glove-finger, presents a coarsely pitted 

 appearance, the significance of which will appear during the description of the histology of the plug. 



STRUCTURE AND COMPOSITION 



The radiograph, PL XIV, fig. 1, and the photograph of the bisected specimen, PI. XIV, fig. 2, of the wax 

 plug show that its constituent material is differentiated into two distinct components, one of which can 

 be regarded as the outer covering and the other as the core of the plug. The outer covering comprises the 

 whole of the attenuated distal end of the cone as well as the thin, superficial layer which surrounds the 

 base and extends round the outside of the latter's skirt-like margin. The cut face of this component of 

 the plug is marked by a number of coarse striations, which run approximately parallel with the long 

 axis of the cone. 



The core is a more bluntly conical structure and forms the greater part of the stout, basal part of the 

 plug, its concave mesial aspect being contiguous with and fitting over the lateral end of the glove- 

 finger. Examination of the cut surface shows that the material of the core is arranged in a series of 

 conspicuous laminations, those nearest the base being concentric with the latter, and approximately 

 semicircular in form. More distally the laminations become thicker and semi-eliptical, and eventually 

 sharply convex to conform in shape with the apex of the cone. The whole series of laminations appears 

 as a number of alternate bands of light- and dark-coloured material, the colours being the macroscopic 

 expression of an alternating histological structure. 



Microscopic examination shows that the two components just described are of different origin, the 

 outer covering being derived from the lining of the meatus and the core from the external surface of 

 the glove-finger. PL XV, fig. 4, which is a photomicrograph of a transverse section taken from the 

 apex of the outer covering of the plug, shows that the name ' wax plug ' is really a misnomer, since the 

 lipoids, which have been dissolved out of the section, occupy only a small part of the total bulk of 

 material. The principal mass consists of a very large number of layers of squamous epithelium arranged 

 in sinuous folds which appear to correspond in position with the longitudinal ridges on the internal 

 wall of the auditory meatus. The squamae of epithelium are all fully keratinized and show none of the 

 earlier stages of cellular change which are normally to be found when this type of epithelium is 

 examined in situ on the epidermis. 



The photomicrographs, PL XVI, figs. 1 and 2, are of transverse and longitudinal sections respectively 

 of the basal part of the core of the plug. The transverse section shows the squamous epithelium arranged 

 not in sinuous folds but in a mosaic of irregularly shaped islets separated from each other by a reticula- 

 tion of apparently empty spaces. Each islet, PL XVII, fig. 4, consists of a central mass of fusiform cells 

 with large degenerate nuclei surrounded by a number of concentrically arranged layers of a homo- 



