TONGUE OP ORNITHORHYNOHUS PARADOXUS. 457 



of the region, but they are never numerous or distinct. Con- 

 nective-tissue corpuscles are often found between the cells of 

 the epithelium, having intruded from the mucosa ; but this 

 phenomenon is better marked in another part of the tongue 

 (although otherwise similar), where it will be described in 

 detail. The smooth epithelium beneath the tip of the tongue 

 is similar to that just described, with few papillary processes. 

 Its lowest cells contain pigment granules. 



This epithelium must be highly sensitive, as the mucosa 

 beneath it is richly supplied with tactile end-organs, to be de- 

 scribed in connection with the papillae. This anterior sub- 

 region is the most glandular part of the tongue, and in the 

 region of the tip the gland-tubes occupy far more space than 

 the muscle-fibres (fig. 3). The gland-tubes ramify between 

 the muscle-fibres in the whole thickness of the organ for a dis- 

 tance of 5 ram. from the tip. Posteriorly to this point they are 

 not found at the lower surface, but at the posterior limit of this 

 subregion they form a layer more than 2 mm. thick beneath 

 the upper surface, becoming slightly thicker in the posterior 

 subregion, where they finally disappear about 10 mm. in front 

 of the junction with the overhanging surface. The gland-tubes 

 which end csecally without dilatations, are very large, and take 

 an independent course for long distances among the muscle- 

 fibre bundles, not branching frequently. They are not united 

 together into any distinct gland (figs. 2 and 4). The cells have 

 suffered a little by the time that elapsed before the organ could 

 be hardened, but they are easily recognisable as belongino- to 

 the " mucous" type of Klein. They are transparent tall 

 columnar cells, staining very slightly in picro-carmine and 

 borax carmine, deeply in logwood. The walls of the ducts are 

 for a short distance composed of several layers of cells con- 

 tinuous with the lower cells of the superficial epithelium. The 

 lumen of the duct is very narrow during the passage throufrh 

 the epithelium to the surface, but it rapidly expands below, 

 and is at once continuous into a gland-tube of usual struc- 

 ture. The opening on the surface is very slightly funnel- 

 shaped. The ducts very commonly run in little groups of three 



