312 THE DEVELOPMENT OF THE CHICK 
onic intestine, we may next note a few details concerning some 
of its divisions. The history of the mesenteries is considered in 
Chapter XI). 
(Esophagus. Owing to the rapid elongation of the neck the 
cesophagus quickly becomes a long tube. On the sixth day its 
lumen becomes very narrow, and on the seventh day completely 
occluded immediately behind the glottis, owing to proliferation 
of the lining cells. On the eighth day the occluded portion 
Fig. 181. — Photograph of a transverse section through the cesopha- 
gus and trachea of an 8-day chick. 
Cop. H., Copula of the hyoid. Qés., Gisophagus. Tr., Trachea. 
Ven. jug., Jugular vein. 
extends only a short distance behind the glottis: it is com- 
pressed dorso-ventrally and extended laterally throughout the 
occluded region (Fig. 181). On the eleventh day it is open again 
along its entire length. The crop arises as a spindle-shaped dila- 
tation of the cesophagus at the base of the neck; on the eighth 
day it is about double the diameter of the parts immediately 
