PROPORTIONS OF THE TECTORIAL MEMBRANE 13 



to deeply penetrate the membranous labyrinth. A pair of very 

 fine pointed, small bone forceps was found better for this than a 

 drill-pointed needle. Even with fluids which decalcify as slowly 

 as those used, the carbonic acid gas usually forms within the 

 labyrinth faster than it can transfuse, and the resulting pressure 

 of the confined bubbles will press the tectorial membrane upon 

 and over the spiral organ, often pressing it in places beyond 

 semblance of its normal shape and position. Such pressure may 

 be relieved through a very small hole in the bone. Here, the holes 

 were usually made immediately after return from the slaughter- 

 house, holding the cochlea down in a Petri dish under the dis- 

 secting microscope and in sufficient of the fixing fluid to cover it. 



Of the several fixing fluids tried, two were found to give the 

 best results both with cochleae to be teased and cochleae to 

 be embedded for sections. A fluid was desired which would 

 serve both as a fixing and a decalcifying fluid and which would 

 produce neither shrinkage of the tectorial membranes nor swell- 

 ing. Gilson's mercuro-nitric mixture, for example, invariably 

 gave distorted membranes in cochleae of late fetuses and of the 

 adult, though fair preparations in sections of cochleae from quite 

 young fetuses were obtained after it. The very small percent- 

 age of alcohol contained in this mixture was not deemed suffi- 

 cient to produce the distortion by extraction of water from the 

 membrane, but some other of its actions did prove unsatisfactoiy 

 with the older stages. Decalcification after fixation by various 

 fluids was tried with discouraging results. With both the nitric 

 and hj^drochloric acid decalcifying fluids, proven with other 

 material, either maceration or distorting shrinkage efi"ects re- 

 sulted in the preparations. Decalcification after embedding 

 the fixed cochlea in celloidin gave better but not satisfactory 

 results. The celloidin imprisons bubbles of gas both within 

 as well as outside the cochleae and those imprisoned within 

 distorted the tectorial membrane in numerous places along its 

 extent. 



Zenker's fluid and the fluid employed by Held ('09) gave the 

 best results. In Zenker's fluid, the swelling action of the acetic 

 acid in it, causing the tissues to take up water, seems to be coun- 



