Fig. 25. Diagram of the tracheal bud from the ventral aspect of the foregut. 

 The former presents mitotic figures following the path of a right-handed 

 helix. The latter presents mitotic figures following the path of a left-handed 

 helix. The tracheal or lung bud is an outgrowth from the ventral aspect 

 of the cephalic aspect of the entodermal foregut. The cause of the mitosis pur- 

 suing a path of a right-handed helix in the trachea is due to the deflection of the 

 left-handed, helicoidal, mitotic path of the foregut. This deflection occurs at 

 the cephalic orifice of the tracheal epithelial tube where it arises from the floor of 

 the entodermal tube of the foregut. 



78 



