126 Irving Hardest}' 



publishes some very misleading photographs of vertical sections of the 

 cochlea, made some of his observations from isolated bits of the 

 membrane teased free in fluid, and probably these bits suggested to him 

 the greater difference in the width of the outer portion in the two 

 regions. Obviously, measurements of the membrane from sections, 

 necessarily treated with alcohol, etc., and therefore shrunken, would 

 average less and be less regular than if taken from teased and un- 

 shrunken specimens, and, as may be seen from Fig. 1, such results 

 depend materially upon the particular localities at which measurements 

 of the free zone are taken. Xone of the literature I have consulted 

 indicates the successful isolation of appreciable lengths of the tectorial 

 membrane of any animal. 



Fig. 1 illustrates the shape of the pig's tectorial membrane as seen 

 from the under surface and with the coil slightly opened, and it is an 

 attempt to indicate its appearance under low magnification. In its 

 natural position in the cochlea, it is more closely coiled, and, especially 

 in the apical turns, the outer edge of one turn appreciably overlaps the 

 inner edge of the turn below it. Thus it was necessary to draw it less 

 closely coiled in order to show it entire. When mounted in glycerine, 

 the cover-glass presses the apical coils of the membrane together and 

 radially outward from the center. The basal coils could not be induced 

 to retain their coresponding curvature with the application of the cover 

 glass, though carefully arranged in the glycerine beforehand. Therefore, 

 it should be stated that none of the preparations obtained showed the 

 membrane as evenly coiled as it is shown in Fig. 1. In making this 

 drawing, the character and extent of the coil was taken from the labium 

 vestibulare laid bare under the dissecting microscope, after the removal 

 of the membrane, and from the appearance of the membrane resting 

 upon the bottom of the dish in fluid. A coiled line was drawn repre- 

 senting the inner edge of the membrane and imitating the character of 

 the coil of the cochlea, but opened sufficiently to avoid overlapping of 

 the edges of the membrane. Then radially from this line, the width 

 of the membrane at each half turn, obtained by measurement of the 

 actual specimen, was indicated by dots. The character and dimensions 

 of the ends and the lines of demarkation of the under surface were 

 likewise sketched in from measurements and from the study of mounted 

 specimens. The scale decided upon gave each space of the ocular 

 micrometer the value of one millimeter. The outline being made, the 

 width and variations of the different zones were determined and other 



