TONGUE OF ORNITHORSYNOHUS PARADOXUS. 459 



in front, whose inclination backwards would prove a further 

 obstacle. Thus the anterior surfaces are tactile and adhesive, 

 while the posterior are chiefly of mechanical use. 



The tactile end-organs mentioned above form a new ter- 

 minal organ, apparently nearly allied to Pacinian corpuscles. 

 The shape is oval or fusiform, and the poles are often slightly 

 flattened. They are very small, as is seen by the highly mag- 

 nified fig. 5 (405 diameters). The corpuscle is surrounded by 

 a laminated investment formed of 6 — 8 extremely thin con- 

 centric layers. There was doubtless an intervening fluid 

 between these capsules during life, as they are now found in a 

 very collapsed and crumpled condition. The number of cap- 

 sules is very uniform, together with the general appearance 

 and size of the corpuscles. Betv/een the capsules occur a few 

 relatively large oval granular nuclei (fig. 5). As in Pacinian 

 corpuscles the capsules constitute the chief mass of the bodies. 

 There is an axial, longitudinally, striated fusiform mass, and 

 an examination of transverse sections with high powers (-pg- oil 

 immersion of Zeiss) showed that this also contains a central 

 column of different structure. A single medullated nerve-fibre 

 terminates in each body, losing its medulla on entrance, the 

 axis cylinder being continuous with the spindle. The cor- 

 puscles are extremely common in the papillae; it is quite usual 

 to find three in a section of a single papilla, and more than 

 once I have seen five (fig. 4). Corresponding to this abund- 

 ance of end organs the papillae are richly supplied with medul- 

 lated nerve-fibres. The corpuscles always occur close to the 

 lowest layer of the epithelium, and never any distance below 

 this. They are never situated in the secondary papillary pro- 

 cesses although they may be close to the bases of these. The 

 long axis of the body is nearly always parallel to the lower 

 surface of the nearest epithelium. Groups of two or three 

 bodies are very common, and sometimes a nerve-fibre appears 

 to pass through one body into another, although in some 

 instances careful examination shows that such is not the case 

 when two corpuscles are arranged in a line, with their apposed 

 ends almost in contact. 



