174 Irving Hardesty 



the walls of the lab3a'inth. Grasped in the forceps, long strips of it 

 can be removed intact, so easily does it come aAvay. Therefore, sound 

 waves passing in the scala vestibuli may be readily imparted to the 

 endolymph in the cochlear dnct. 



Summary. 



(1) The tectorial membrane of the pig, occupying a cochlea of about 

 four turns, has an average length of 25.5 millimeters. It is about 

 three times as broad and five times as thick in the apical half-turn as 

 it is in the last half-turn, its dimensions decrease gradually from its 

 apical toward its basal end, and its ends terminate bluntly. 



(2) Its specific gravity is but little greater than that of the fluid in 

 .Avhich it lies. 



(3) It possesses a small amount of elasticity, barely sufficient to 

 cause the thicker, apical region to resume its normal coils while the 

 membrane is suspended in fluid after being freed from its attachment. 

 Its greater elasticity is in the direction opposed to stress applied longi- 

 tudinally. It is remarkably flexible to stress applied transverse to its 

 long axis. 



(4) Its structure consists of multitudes of delicate fibers of unequal 

 length embedded in a transparent matrix of a soft, collagenous, semi- 

 solid character with marked adhesiveness. The general transverse direc- 

 tion of the fibers inclines from the radius of the cochlea toward the apex, 

 which inclination is greater in the upper than in the under surface. 

 Most of the fibers, by coursing and curving through the membrane, take 

 part in producing the fibrous appearance of both the upper and under 

 surfaces. 



(5) From the study of both its adult structure and the processes by 

 which it is developed, it is concluded that none of its fibers extend the 

 entire width of the membrane, none are attached at both ends, and the 

 greater number of them are attached at neither of their ends. 



(6) Hensen's stripe is explained as a line of the intercrossing ends 

 of the fibers of the under surface resulting from the processes by which 

 the growth of the membrane terminates. 



(7) From its study in both the fresh condition and in preparations 

 considered least shrunken and distorted, it is concluded that the tec- 

 torial membrane projects free over the organ of Corti and is attached 

 only along its inner zone upon the labium vestibulare of the spiral 

 limbus. 



