UN '1 I III INN! I; (.lilOl l.\\ IK. 



321 



^< hk.- purated from the over- 



lying portion of the alimentary tube by t\\ nLv> ; tliis 



furnisho the lir.M indication of a dillerentiat i<>n into u'Mjphagu- 

 trachea (lig. 1M ). Then there -i..\v nut from the enlarged post- 

 eads of the groove (figs, 1*1. L63)two mudl MLCS (Z?) toward the two 

 M les of the body (in the Chick in the ini<lllu <>t' tin- third div), the 



fiiinlanu'iits <>t' the ri^'lit 

 andlt-t't huii:. Mn\ eloped 

 in a thick layer of em- 

 hrvonic connective 

 tissue, they are in im- 

 mediate contact behind 

 with the fundament of 

 the heart ; laterally they 

 project into the anterior 

 ti SMI re-like prolongation 

 (f the body -cavity. 

 With this the essential 

 parts if the re- juratory 

 apparatus are e>tal>- 

 li>l.ed; at this sia-v 

 in amnintie Vertebrates 

 they resemble the simple 

 >ac like st met ure> which 

 the lungs of Amphibia 

 present permanently. 



In the further course 

 of development the fun- 

 daments of trachea and 

 oesophagus, which com- 

 municate by means of a 

 Insure, become separated 

 by a constriction which 

 begins In-hind, where the 



pulmonary sacs have budded OU< dually m- 



constricting oil is heiv interrupt-d at the place which becomes the 

 entrance to the larynx. The latter i> di>;in.i:ui>liabl.' in the case of 

 Man at the end of t he tilth week as an : ut at the In^ii. 



of the fundament of the trachea. It acquires its cartilages ii, 

 eighth or ninth w<- ; -k. of th.-.M-thi- thyroid cartilage arises, according 

 ti the oomparati ve-anatomical v . tiom a fusion 



21 



Fig. 181. Alimentary tube of a human embryo (A . 



5mm. long, neck meacuremen- . " Meusch- 



li.h.- Kin>>ryonn." Mn^ .netcrs. 



^land ; 



C/i, chui.i | to the la; 



l>ancras; Lby, ir 

 kof theinti 

 All, allai. 



it of it ; 1), bnna ]- 



