404 



THE SKIN AND THE SENSE-ORGANS. 



nerve contain medullated fibres of various dimensions and bipolar, 

 spindle-shaped ganglion-cells. The nerves pierce the walls obliquely 

 or vertically, and retain their medullary sheaths until near their 

 final distribution. On each of the nerve-terminations is found 

 nerve-epithelium, which varies in height in different parts. In the 

 crista acustica it measures 0*075 mm - in height in the middle part, 

 0*06 mm. at the sides on the macula rec. utriculi 0*09 mm., on the 

 macula sacculi 0*075 mm., on the papilla lagenae 0*06 mm., on the 

 papilla part, ba^il. 0*045 mm., on the macula neglecta 0*075 mm. 

 The epithelium is of two kinds, hair-cells and sustentacular cells. 



Fig. 252. 



The nerve-terminations in the membranous labyrinth of Rana esculenta ', after Retzius. 

 I. Vertical section through the crista acustica of the anterior ampulla. Verick's Syst., Obj. ITT, 



Oc. 3. 



II. Vertical section through the macula ac. recessus utriculi. Verick's Syst., Obj. VIII, Oc. 3. 

 III. Three isolated hair-cells from the crista ac. of the anterior ampulla. Verick's Syst., Obj. VIII, 



00.3. 



IV. Two isolated sustentacular cells from the crista ac. of the anterior ampulla. Verick's Syst., 

 Obj. VIII, Oc. 3. 



cr Crista acustica. 

 CM Cupula terminalis. 

 fz Sustentacular cells. 

 A Hairs of hair-cells. 

 hz Hair-cells. 

 n Nerve-fibres. 



a. The hair-cells (Fig. 252 hz} have, on the whole, elongated, 

 flask-like forms, but are not all of the same length (0*024-0*04 mm.). 

 The free ends of the cells are rounded, flattened, and yellowish, and 

 each bears a stiff cilium, which is fixed by a broad base to the cell, 

 and thins out towards its free end : the cilia vary in length ; in the 

 ampullae their greatest length is 0*13 mm., on the macula rec. 

 iitriculi 0*011 mm., and on the papitla lagenae 0*017 mm. The 



