THE MICROSCOPE IN ANIMAL HISTOLOGY. 223 



called from its discoverer the organ of Corti, is found. 

 Kolliker considers the free position of the expanded por- 

 tion of the nerve, and the extent of surface over which 

 its terminal fibres are spread, to constitute it an organ of 

 great delicacy, enabling us to distinguish several sounds 

 at once and to determine their pitch. There is a striking 

 analogy between the visual and auditory apparatus in the 

 ganglionic structure of the nerve-structure. Plate XXIV, 

 Fig. 179, represents a vertical section through the tube 

 of the cochlea; and Plate XXIY, Figs. 180 and 181, the 

 vestibular aspect and a vertical section of Corti's organ. 



Waldeyer recommends examination of the cochlea in a 

 fresh state and in aqueous humor. Preparations in osmic 

 acid and chloride of gold are also useful. For sections he 

 removes much of the bony substance of large cochleae with 

 cutting pliers, opens the membrane in several places, and 

 places the specimen in 0.001 per cent, of chloride of palla- 

 dium, or 0.2 to 1 per cent, osmic acid solution for twenty- 

 four hours, then for the same time in absolute alcohol. 

 It is then treated with a fluid composed of 0.001 per cent, 

 chloride of palladium with one-tenth part of J to 1 per 

 cent, muriatic or chromic acid, to deprive it of earthy 

 salts. It is then washed in absolute alcohol, and inclosed 

 in a piece' of marrow or liver, and placed to harden in 

 alcohol again. The hollows of the cochlea may be filled 

 with equal parts of gelatin and glycerin before they are 

 inclosed. Sections must be cut with a sharp knife. 



Rutherford advises the softening of the bone and hard- 

 ening of other tissues by maceration in chromic acid and 

 spirit (1 gramme of chromic acid in 20 c.c. of water, and 

 180 c.c. of methylated spirit slowly added). For sections 

 he commends Strieker's mode of imbedding in gum. Place 

 the cochlea in a small cone of bibulous paper, containing 

 a strong solution of gum arabic, for four or five hours ; 

 then immerse the cone in methylated spirit for forty-eight 



