398 URBAN PRITCHAUD. 



We have yet to draw a distinction between the prosenchy- 

 matous cells (stereides) which belong to the bundles and those 

 which belong to the ground tissue^ by means of which we 

 may be able to refer any stere'ide to its proper morphological 

 position. Such a difficulty does not arise with reference to 

 the woody fibres, or in the case of certain of the forms of 

 prosenchyma occurring in the ground tissue (Hypoderma, 

 Collenchyma) — their position is generally sufficient to indi- 

 cate their real nature — but it exists especially in the case of 

 the bast fibres. An investigation of their structure gives no 

 characteristic which might serve to distinguish the bast fibres 

 which belong to the ground tissue (external sheath) from 

 those which belong to the bundles (hard bast). We must 

 remember, however, that those cells which form the external 

 sheath are necessarily outside the bundle sheath, and are, 

 therefore, ground-tissue elements (PI. XXYII, fig. 1), 

 whereas all those -which lie Avithin this sheath belong to the 

 vascular tissue. In those plants which have no bundle 

 sheath the bast fibres which are adjacent to the bundles 

 must be regarded as belonging to them. 



The Termtnation of the Nerves in the Vestibule and 

 Semicircular Canals of Mammals. Read before the 

 British Association, Glasgow, September, 1876, by 

 Urban Pritchard, M.D., F.R.C.S., Aural Surgeon to 

 King's College Hospital, Lecturer on Animal Physi- 

 ology, King's College, London. (With Plate XXVIIL) 



In this paper I propose giving the results of my investi- 

 gations into the structure of the nerve-epithelium, as it is 

 called, which contains the terminal distribution of the 

 acoustic nerves in the vestibule and semicircular canals. 



Up to the present this structure has been chiefly studied 

 in the cold-blooded vertebrates and birds ; and the various 

 observers (including Max Schultze, Kolliker, Odenius, Hasse, 

 Riidinger, Ebner, and Meyer), although they agree as regards 

 certain general points, yet appear to differ considerably 

 respecting many important questions. 



Having been fortunate enough to make some very suc- 

 cessful preparations of this nerve-epithelium in the adult 

 and foetal cat, which to my mind throw considerable light on 

 the subject, I have ventured to lay before you the results of 

 these observations. 



