THE SK1X AND THE SENSE-ORGANS. 



perichoiidrium lining this cavity form a very delicate, pigmented 

 membrane, formed of numerous fine elastic fibres which cross each 

 other irregularly; its inner surface is lined with an incomplete 

 layer of branched protoplasmic cells with large oval nuclei. From 



Fig. 245. 



I ff 



dp S3?S ' = Y~^ *% 



cf-i 



The membranous labyrinth of liana esculenta, within its natural covering 

 after Retzius. 



I. Seen from the side ; magnified ten times. 



II. The hinder half ; magnified ten times. Seen obliquely from above, and in front, and from 



the side. 



rt(( Anterior ampulla. 



adf Apertura fenestrae ovalis. 



al. Apertura lagenae. 



ap. Posterior ampulla. 



apb. Opening into the pars basilaris. 



ca Anterior semicircular canal. 



ce External semicircular canal. 



ep Posterior semicircular canal. 



dfo Ductus fenestrae ovalis. 



dp Ductus perilymphaticus. 



<ll>' Saccus perilymphaticus. 



I. Lagena cochlea. 



ms. Macula sacculia. 



pb Pars basilaris cochleae. 



/x:r Wider part of perilymphatic space. 



per 1 Narrower part of perilymphatic space. 



ru. Ramus anterior. 



>>!. Ramulus neglectus. 



'/'. Ramus posterior. 



#. Ramulus sacculi. 



s. Saccule. 



sfo Saccus fenestrae ovulis. 



spl Saccus perilymphaticus. 



tv Tegmentum v;isculosum. 



Utricle. 



this membrane numerous irregular bundles of fibres, in the form of 

 trabeculae, pass into the space and form a rich network, which is 

 attached internally to the outer surface of the membranous labyrinth 

 and holds it in position. Free nucleated leucocytes are occasionally 

 met with in the meshes of this network. The perilymphatic space 

 is prolonged into two subsidiary cavities : 



(i) The ductus fenestra ovalis (Retzius), (Fig. 245 dfo) com- 

 mences as an opening (adf} immediately opposite the foramen ovale 

 of the hard capsule, which leads into a moderately large canal, the 

 structure under consideration. It passes forwards and outwards 

 through the fenestra ovalis between the interstapedial and the outer 

 wall of the capsule into the oval depression (fossa fenestrae ovalis}, 



