EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 



15 



arated from the main cartilaginous mass of the capsule by a 

 surrounding zone of precartilage and intervening between the 

 latter and the duct is a narrow zone of mesenchymal tissue 

 which is somewhat reticular in character. This zone of reticulum 

 has attained its greatest width on the median side of the duct, 

 toward the right, being at this point about twice as wide as the 



rDu.ctus semiclrc. lat. 



•i^Precartila(^e 



-^r-^. — Reticuki m 



' . ■ .''■ ■ " A!'. ' ■ . ■ ■ 



Fig. 8 Section passing transversely through the lateral semicircular canal 

 in a human fetus 43 mm. long (Carnegie Collection, No. 886). Enlarged 100 

 diameters. The epithelial semicircular duct is larger in diameter than the one 

 in figure 9, but that is the accidental result of its having been fixed while in a 

 distended condition. The size of these ducts cannot be compared without tak- 

 ing account of this variation in their distension. 



thickness of the duct wall. It is characterized by its reticular 

 arrangement and by the presence of small blood vessels which 

 are not found in the precartilage, although they lie closely against 

 its inner margin. The area of precartilage stands out con- 

 spicuously in material that has been intensely stained in hema- 

 toxylin without any counter-stain. A series of this kind is rep- 

 resented by No. 199 in the Carnegie Collection. In that series 



