30 



THE HISTOGENESIS AND GROWTH OF THE OTIC CAPSULE AND ITS 



lines. The precartilage in turn is gradually dedifferentiated into the periotic retic- 

 ulum. In this way the margin of the true cartilage gradually recedes from the 

 epithelial duct, and the last of the precartilage 

 is eventually dedifferentiated into a reticulum. 

 Along with the process of excavation of car- 

 tilage there must go the laying-down of new 

 cartilage. For instance, as the lateral cartila- 

 laginous canal enlarges it also moves laterally, 

 so that the distance between it and the carti- 



Reticulum 



Precartilaqe 



xi 



: - 



*,y: ' K) . ^ ,-* 



Carlilaqe 



FlGCRE 2. 



FIGURE 3. 



Fit;. ~. Detail of the lateral semicircular duct in a human fetus 30 mm. long (Carnegie Collection, No. 86), being the 

 same as that shown in figure 11. The section is 50ju thick and is enlarged 470 diameters. It shows the 

 epithelial wall of the duct and the character of the surrounding tissues that lie between it antl the cartilage. 



1 K. :'.. --Detail of the lateral canal in a human fetus 46 mm. long (Carnegie Collection, No. 95, slide 72, section 1). 

 This is the same canal as that shown in figure 15. The section is lOOji thick and is enlarged 470 diameters. 

 By comparing it with figure 2 one can see how the cartilaginous canal is enlarged by the dedifferentiation of 

 cartilage into precartilage and the precartilage in turn into the periotic reticulum. 



