44 IRVING HARDESTY 



T.\BLE 4 



Giving in micra averages of the thickness of the spiral organ (of Corti) as found 

 for the pig in the various stages of development and the regions of the coil of the 

 cochleae specified 



turn. The cochlea from which figure 9 was made came from 

 a pig of 22 cm. and the two of this stage measured for the results 

 recorded in table 4 were chosen from this lot of pigs. The spiral 

 organ was some thicker in one of the two than in the* other. The 

 variations in the thickness of the 7th half turn, shown in table 

 4, are due largely to the varying distances from the actual basal 

 end of the organ at which the plane of section passed, for at 

 19 cm., in my specimens, the differentiation of the organ in the 

 basal region is about completed. Examination of the various 

 stages, and the measurements, show that with the beginning of 

 the differentiation of the spiral organ from the lesser ridge, the 

 organ begins to increase in thickness throughout the cochlea, 

 and that, though the increase takes place most rapidly in the 

 stages before full term, it seems to continue after birth. The 

 increase is greatest in the apical end. 



The growth increase in the width of the organ could not be 

 accurately measured in the 1st and 3rd half turns till above pigs 

 of 22 cm., because, as shown in figure 9, its differentiation was 

 not complete. It is usually completed throughout in pigs of 

 full term. The varying width of the organ in the adult is given 

 in table 3. 



As suggested in the figures, the cells of the greater epithelial 

 ridge finally all sink till they are represented only by the rela- 

 tively few, broad, fattened cells lining the internal spiral sulcus. 

 The outermost five to eight of the cells of the greater ridge re- 

 tain a portion of their high cylindrical form and become the 



