192 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



the works quoted at the end of this note under the numbers 58 65, 

 with which are to be classed the communications of Huschke (28), 

 Reissner (46, 47), Kolliker (34), Hensen (27), Hasse (21), Bottcher 

 (4), Rosenberg (49), and Middendorp (40). A few points have been 

 mentioned in the text, but a continuous account of the development of 

 the cochlea can scarcely be at present given. 



METHOD OF INVESTIGATION. It is unnecessary that I should again 

 recommend the investigation of the cochlea to be undertaken whilst 

 perfectly fresh in the aqueous humour. Equally good results, or even 

 still better, on account of the somewhat greater sharpness of the 

 contours, are obtained from the employment of perosrnic acid, which I 

 can recommend as being just as good for the cochlea as for the retina. 

 It can be used in the form of solution, containing from one-tenth to 

 one per cent. The former strength is the best for recent prepara- 

 tions, torn with needles ; the latter for hardening specimens. Solutions 

 of common salt, varying from one quarter to one half per cent., are 

 also very serviceable for preparations teazed out with needles. The 

 pillars of Corti can best be isolated in solutions of chromic acid, con- 

 taining O05 per cent., in which also the hair cells are well preserved. 

 Chloride of gold may be applied with advantage in solution in the 

 proportion recommended by Cohnheim for the cornea, as well as 

 nitrate of silver in one per -cent, solution, the latter being especially well 

 adapted for the spiral fibres. I would recommend the following plan 

 for the preparation of good sections. As much osseous substance as 

 possible should be removed from large cochlesd with cutting pliers, and 

 two or three small openings should be made into this cavity ; smaller 

 cochlea should be allowed to remain unopened. The cochleae must then 

 be macerated for twenty-four hours in a proportionately large quantity 

 of solution of chloride of palladium, containing O'OOl per cent., or of 

 perosmic acid, containing 0*2 per cent, (for smaller cochleae) or 0'5 1 

 per cent, (for larger). The specimens are then placed in absolute 

 alcohol for twenty-four hours, or they may be immersed at once in the 

 decalcifying fluid. The best decalcifying fluid is chloride of palladium 

 (O001 per cent.), with one-tenth part of hydrochloric acid, or one- 

 fourth one per cent of chromic acid. After the process of decalcifica- 

 tion is completed, the cochleae must be washed with absolute alcohol, 

 and then imbedded in fresh spinal cord or in liver. For large cochleae, a 

 corresponding piece can easily be cut from the latter. The specimen, 

 with its enclosing material, is once more placed in absolute alcohol. 

 As hardening proceeds, the latter contracts so firmly upon the cochlea 

 that this lies immoveably in position, and can be conveniently divided 

 into the finest sections. The cavities of the cochlea may be filled 



