AND THE CRISTA SPIRALIS OF THE COCHLEA. 59 



or two days in the second or third fluid, the pieces were washed in running water 

 and hardened for many weeks in 70 per cent alcohol with some drops of iodine. 

 The iodine effectively acts as a mordant. Where necessary, decalcification was 

 completed by 2 per cent nitric acid in 70 per cent alcohol. 



Before embedding in paraffin the pieces were stained by borax carmine. The 

 series was then stained by iron hematoxylin, Congo red, and light green. In 

 advanced stages of development the best results were usually obtained by the 

 following treatment : 



1. Immerse one day in 2.5 gm. ferric alum in 100 c.c. distilled water. 



2. Wash one second in distilled water. 



3. Immerse for some minutes in a solution of Congo red, 1 gm. in distilled water 



200 c.c. 



4. Wash in distilled water. 



5. Immerse one day in a 0.5 per cent aqueous solution of crystallized hematoxylin. 



6. Decolorize by a 1 per cent aqueous solution of ferric alum. 



7. Wash for one hour in running water. 



8. Stain for some seconds in a solution of 0.5 gm. light green in 200 c.c. of 95 per 



cent alcohol. 



9. Treat in succession with absolute alcohol, xylol, and Canada balsam. 



By this method the nuclei, the central corpuscles, and the terminal bars are 

 stained very dark blue, the cytoplasm and its prolongations red, the ground sub- 

 stance of the connective tissue and the membrana tectoria green. 



Mallory's method is also very useful for staining blue the ground substance 

 of the connective tissue and the membrane of Corti. 



The membrana tectoria possesses very delicate structures in which shrinkage 

 and agglutination are provoked by the best fixing agents, although some of my 

 series give results which are good and are confirmed by a new and better method 

 tried during the past few weeks. Before treatment by one of the three fixing fluids 

 mentioned above, I made one or two small openings in the bony wall of the cochlea 

 and exposed the piece for 15 minutes to vapors from an aqueous solution of osmic 

 acid or submerged it in a 1 per cent aqueous solution of the same for one hour. 

 Afterwards fixation was completed by immersion in trichloracetic acid, Bouin's 

 fluid, or Zenker's fluid and the series of sections was stained by iron hematoxylin, 

 Congo red, and light green. By this method some of the turns of the cochlea give 

 very good preparations of the structure of the membrana tectoria. The mito- 

 chondria also are visible within osteoblasts, osteoclasts, connective-tissue cells, 

 all epithelial cells, and the sensorial elements. 



ANATOMICAL SUBSTRATUM OF THE MEMBRANA TECTORIA. 



In spite of numerous investigations many features remain obscure in the histo- 

 genesis and structure of the membrana tectoria, in its connections with the adult 

 organ of Corti, and in its extension beyond the sensorial epithelium. Embryolo- 

 gists almost all agree that the membrana tectoria appears in the earliest stages of 

 development of the membranous cochlea before the appearance of the greater and 

 the lesser epithelial ridges and the crista spiralis, as a kind of very thin membrane 



