168 



TEXT-BOOK OF EMBRYOLOGY. 



Neural crest jk 



Myotome 

 Sclerotome 



Pronephros- - 



Parietal mesoderirr 



Intestine \ : --y.'i^HX-l -^K. ' V.JfcS? -: < * ' ' Umbilical 

 Vein 



-^>- P "^ 



Visceral mesoderm 



FJG. 142. Transverse section of human embryo of the 3rd week. Scl. 1 , Break in myotome at 

 point where sclerotome is closely attached. Kollmann. 



Neural tube -- 



Intersegmental B 



artery 



Intersegmental- - 

 artery 



Ectoderm 



"Sclerotome 



Myocoel 



FIG. 143. Three primitive segments from sagittal section of human embryo of 

 the 3rd week. Kollmann. 



