82 



ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



the pig in a somewhat different way, using the vertical line from 

 the basilar membrane proper through the m'ddle of the outer 

 hair cell to the surface of the organ, and found the increase in 

 thickness to take place most rapidly at the stages before full term, 

 though it seems to continue after birth. I have not made cor- 



TABLE 55 

 Greatest height of Heti sen's supporting cells- on age (chart 25) 



Ratios 1 — 6 days 



1— 12 



1— 20 



1—546 



6— 12 



6— 20 



6—546 

 12— 20 

 12—546 

 20—546 



0.6 

 1.5 

 2.1 

 2.5 

 2.6 

 3.8 

 4.3 

 1.5 

 1.7 

 1.1 



responding studies on the rat. In the latter animal, however, 

 the rapid increase usually appears at twelve days of age, when 

 the animal as a rule first responds to auditory stimuli, and thus 

 we have a correlation between the development of the organ 

 and the beginning of the function, which will be discussed later. 

 In the case of one rat that could hear at nine days this change 

 had already occurred. 



