GUSTATORY ORGANS OF AMPHIBIA. 15 



cells, and is composed of peculiar cells and cell-like bodies. 

 The lateral surfaces of the papillse are covered with simple 

 non-ciliated columnar epithelium. 



The connective-tissue body of the papilla consists, in its in- 

 ferior and larger part, of rather loose connective tissue, in which 

 are imbedded vascular capillary loops, muscular fibres branched 

 at their extremities, and a fasciculus of dark-bordered nerves. 

 The upper part is a solid disk, O01 0'015 of a millimeter in 

 thickness, composed of very dense non-nucleated connective 

 tissue, to which the name of nerve cushion may be applied. It 

 forms the floor upon which the gustatory disk rests. 



From five to ten dark-bordered nerve fibres enter from 

 below into the papilla, and run in its axis almost always 

 unbranched as far as to the inferior surface of the nerve cushion. 

 At or just before their entrance into the latter, they become 

 somewhat attenuated, and lose their medulla and their neuri- 

 lemma. Immediately after this they divide, and appear as very 

 fine (about 0'002 of a millimeter in diameter) and pale nerve 

 fibres, which, after repeated dichotomous division, form a deli- 

 cate and close nervous plexus which is expanded nearly hori- 

 zontally in the inferior half of the nerve cushion. From this 

 plexus, numerous fine twigs (fig. 277), again dividing, ascend in 

 a straight or oblique direction, as far as to the surface of the 

 nerve cushion. They here enter into connection with the ele- 

 ments now to be described of the gustatory disk. 



The nerve fasciculi that enter the papillae fungiformes arise from 

 the glosso-pharyngeal nerve. The small papillae of the Frog's tongue, 

 which are covered with ordinary epithelium, appear, as Billroth has 

 already stated, to be destitute of nerves. The nerve cushion, which 

 inferiorly becomes firmly fused with the remaining connective tissue 

 of the papillae, but presents externally a sharp and smooth surface, 

 consists of very dense indistinctly fibrillated connective tissue, which 

 in diluted acids and alkalies swells up less strongly than ordinary 

 fibrlllar connective tissue. Key regards the nerve cushion as a colossal 

 expansion of the neurilemina, and names it the nerve capsule. 



The pale nerve fibres, into which the dark -bordered break up at 

 their entrance into the nerve cushion, were first seen by Key. He 

 admits, however, a more brush-like division of the nerve fibres into 

 very fine varicose branches, and lias not observed the frequently occur- 



