On the Perilymphatic Spaces of the Amphibian Ear. 225 



narrow in some forms, wider in others (figs. 1 — 12, D. P.), passes 

 across by a more or less convoluted course to the inner wall of the 

 capsule, and runs through into the cavum cranii by an aperture just 

 posterior to that for the posterior branch of the auditory nerve (figs. 1, 

 6, 7). We may call the duct, the ductus perilymphaticus, one of the 

 names given to it by Hasse [5], i-ejecting his alternative term of 

 "aquaeductus cochleae". His use of the name "foramen rotundum" for 



Cavnm cranii 



Siuii.'! superior utriculi 



Sa«r-..^^-.WT»^^jq^^ 



Pars neglecta , 



Ductus perilymphaticus 



Canalis lateralis 



Recessus partis iieglectae 



Recessus 



partis basilaris 



di- . , ''"" //Ir * T ' ^0^~ Spatium sacculare 



Spatmni menmgeale _^ \- y/ f tA \ //// ^ 



Fenestra vestihuH 



1 Sacciilus 

 Lagena 



Diagram 1. 



Transverse section through auditory capsule of a Urodele, compoimded of a series 

 of sections. The pars basilaris is seen at the upper end of the lagena. For con- 

 venience the pars neglecta is shown separated from the sacculus. The areas of 

 contact between the walls of the perilymphatic spaces and the tympanal areas of 

 the sacculus, pars neglecta and pars basilaris are shown as fine lines. Perilym- 

 phatic tissue dotted, except where forming specialized layer of wall of labyrinth or 



perilymphatic system. 



the aperture from the auditory capsule into the cavum cranii can 

 also scarcely be justified by our knowledge of the comparative ana- 

 tomy of the parts concerned. For this aperture the name foramen 

 perilymphaticum is less objectionable. Within the cavum cranii the 

 ductus opens into a space lying between certain layers of the brain- 

 coverings. It is situated in the ventro-lateral angle of the cranial 

 cavity, partly ventral and partly posterior to the root of the auditory 

 nerve. The term spatium meningeale {S. M. fig. 7, 12) will be used for 

 this intra-cranial space. Another well marked and constant space ap- 

 pears as a short and wide diverticulum of the ductus perilymphaticus, 



Internationale Monatssclirift für Anat. u. Pliys. XIX, 15 



