372 



PRACTICAL HISTOLOGY. 



[XXXIII. 



and nitric acid fluid, and harden in the dark in alcohol. Stain the 

 softened cochlea in bulk in borax-carmine. Embed in paraffin, and 

 cut sections from base to apex of the coiled tube. Fix on a slide, 

 and mount in balsam. Use the other decalcified cochlea, stained as 

 above, and cut it in celloidin. 



(ii.) The following is a better method (Ranvier), and preserves 

 the finer structures in situ. Open the bulla of a guinea-pig, and 

 cut out the inner ear. Make an opening or two in the turns of the 

 cochlear tube, and place it in 1-2 cc. of i per cent, gold chloride. 

 Add to the gold solution from time to time a few cc. of the follow- 

 ing mixture : i per cent, gold chloride and a fourth part of formic 

 acid, boil, and allow the mixture to cool. Leave the cochlea in the 

 gold (20-30 minutes), remove it, wash, and expose it to light in 



FIG. 342. V.S. Cochlea of Guinea-Pig. V. Scala vestibuli ; T. Scala tympani ; VT. There 

 the two communicate ; C. Cochlear canal or scala media ; R. Reissner's membrane ; 

 t. Membrana tectoria. 



water slightly acidulated with acetic acid (1-2 drops to 20 cc. water). 

 After 2-3 days harden it in alcohol and decalcify it in picric acid. 

 Embed in gum and harden in alcohol, or embed it in celloidin 

 and make sections parallel to the axis of the cochlea. 



(iii.) After removing the inner CT, open its osseous canal under 

 osmic acid .2 per cent, and leave it in this fluid for 10-12 hours. 

 Wash in water and decalcify in chromic acid, 2 per 1000. 



(iv.) After treating the cochlea with osmic acid and hardening it 

 in alcohol, the following decalcifying fluid may be used : i cc. of 

 a i per cent, solution of chloride of palladium, 16 cc. of hydrochloric 

 acid, and 1000 cc. of water. 



3. V.S. Cochlea, parallel to its axis. 



(a.) (L) The turns of the cochlear tube cut across (fig. 342), each 

 tube divided by a transverse partition the lamina spiralis into 



