298 DISCOVERY REPORTS 



genous or coarsely striated substance which may contain darkly stained flattened nuclei. Encircling 



the whole group of islets can be seen the sinuous squamae of the fully keratinized epithelium of the 



outer covering of the plug. From the macroscopic appearance of the base of the plug it would appear 



that the spaces between the islets were filled with lipoids and that these have been dissolved out of the 



section. 



The longitudinal section, PI. XVI, fig. 2, is taken through the first two concentric laminations of that 

 part of the plug which is contiguous with the glove-finger. Comparing the appearance with that of the 

 transverse section described above it will be seen that the islets constitute the cross-section of a series 

 of columns of tissue which are separated from each other by undulating fissures. The first and second 

 laminae are discontinuous, so that two sets of tissue columns appear separated by a space which is 

 partly filled by a layer of keratinized epithelium. The structure of the tissue is markedly different in the 

 two laminae (PI. XVII, figs, i and 2) the first set of columns containing layers of the type of cells which 

 were distinguished in the transverse sections. In the second lamina the curvature of the tissue layers 

 is completely reversed and the spaces between the columns are partly filled by a great number of 

 squamae of keratinized epithelium derived from the central masses of cells which are more degenerate 

 than those of the first lamina. 



The general structure of the transverse and longitudinal sections of the core of the plug indicates 

 that the epithelium is generated from the numerous small papillae which are plainly visible on the end 

 of the glove-finger. It is unfortunate that no properly fixed material was available for examination 

 of the soft parts of the meatus and glove-finger, and the sections shown in PI. XV, fig. 1 and PI. XVII, 

 fig. 3, show only the corium of these two structures respectively. Ceruminous or sweat glands are 

 virtually absent from the section of the corium of the meatus but very abundant in the section taken 

 through that of one of the papillae on the glove-finger. It is possible that these glands, if present in the 

 meatus, are located in definite areas, although it would not be surprising if they were absent altogether. 

 The ceruminous glands of the glove-finger are even more plentiful in areas other than that shown in 

 the figure. 



The homology of the various structures referred to above is not difficult to find when it is re- 

 membered that the external meatus and the glove-finger (the pars flaccida of the tympanic membrane) 

 are formed from an involution of the epidermis. Considering first the distal part of the wax plug, it was 

 found that the latter was composed of a great number of layers of keratinized epithelium containing no 

 nuclei and that between the layers there was a series of filamentous interstices which were presumably 

 filled with lipoid. This type of structure is characteristic of the whole of the outer covering of the wax 

 plug and apparently constitutes the stratum corneum of the epidermis of the external auditory meatus. 

 Ranvier, according to Gray (1946), found in the stratum corneum of man granules of a substance which 

 had the characteristics of bees-wax. 



Considering next the structure of the core of the plug, it was found that macroscopically the material 

 was divided into a number of discrete concentric laminations and that each lamination consisted of a 

 series of columns of tissue which were presumably generated from papillae on the end of the glove- 

 finger. Each column of tissue in the first lamination consisted of layers of fusiform nucleated cells of a 

 granular appearance followed by homogenous or coarsely striated layers containing darkly stained 

 flattened nuclei, the whole being surmounted by a layer of keratinized epithelium. The entire system 

 of cells gives the appearance of being the strata granulosum, lucidum and corneum, i.e. the zona cor- 

 nea of the epidermis of the glove-finger. The cells show the characteristic appearance associated with 

 progressive keratinization, the granules probably being the intermediate substance eleidin. The sinuous 

 fissures between the columns of tissue are reminiscent of the spirally coiled ducts of ceruminous or 

 modified sweat glands. The second lamination shows the same type of structure except that the cells 



