BY DR. KLEIN. 155 



are then made in succession across the axes of the several 

 canals, and are stained in weak carmine. Such sections, being 

 readily obtained in a perfect state in the foetus, serve as a 

 most valuable key to the study of the adult organ. 



The fully-developed organ is best studied in the ear of a small 

 dog, guineapig, or new-born child. From the fresh jaw of the 

 guineapig the whole of the petrous portion of the temporal bone 

 can readily be removed, and placed for a week or fortnight in 

 a half to a quarter per cent, solution of chromic acid, to which 

 a few drops of hydrochloric acid has been previously added, 

 the liquid being changed once or twice during that time. The 

 cochlea is then removed, and after remaining in spirit for a 

 few days, is filled with a mixture of wax and oil under the 

 air-pump. Sections are prepared as before, after embedding. 

 A second mode should also be employed, which is as follows : 

 A horizontal section is made through the organ after removal 

 .from the spirit, so as to expose all the turns of the cochlear 

 canal. Both halves are then embedded in gelatin solution, to 

 which a few drops of glycerin has been added, as mentioned in 

 Chapter VI. The transparency of the gelatin 'enables us to be 

 sure of the direction of our sections. These are placed first in 

 warm water, to remove the gelatin. They may be then mounted 

 in glycerin, or replaced for a short time in spirit, stained with 

 carmine, and mounted in Dammar. I would, however, advise 

 the student not to risk the manipulation required for the latter 

 process, but to mount in glycerin at once after the warm water ; 

 for the section, if it is as thin as it should be, would stand a 

 considerable chance of injury. 



For the study of the organ of Corti, thin vertical parts of 

 sections must be sought for in which the lamina spiralis near 

 that organ is seen to be cut exactly across: this is more par- 

 ticularly the case when the situation of the rods of the arch of 

 Corti, the arrangement of the cells of Deiter and the ciliated 

 cells, and the distribution of the nerves of the membrana basi- 

 laris, are under examination. To show the elements of the 

 membrana reticularis, and the epithelium of E-eissner's mem- 

 brane, more obliquely cut parts of the section are to be chosen, 

 or even portions where a surface view of these structures is 

 obtainable. 



Organ of Taste. For the stud} 1 - of the organ of taste the 

 tongue of the frog or rabbit may be used. In the former, our 

 attention may be confined to the papillse fungiformes, the most 

 important subject of observation being the topographical rela- 

 tions of their cellular covering. The perfectly fresh organ is 

 spread out with pins on a plate of cork, care being taken to 

 avoid unequal stretching, and placed in very dilute chromic 

 acid. Vertical sections are then made in the usual way. 

 Another way is to color the fresh organ, spread out on cork as 



