216 



Caroline McGill. 



observed the same condition in the mouse embryo, but EUenberger 

 (1884) stated that in the pig-, the first formation is in the very lower- 



A cross section of the oesophagus of a pig embryo 5 mm in length. The section 

 shows the deep pulmonary groove (b) in the ventral part of the oesophagus {a). 

 The primitive mesenchyme is arranged in a syncytium, which forms a very loose 

 network around the oesophagus, but is more condensed around the pulmonary 

 groove. ^ := endodermal epithelium; ^/ = mesenchyme cell; c = protoplasmic bridge. 

 Fixation, Zenker's fluid. Stain, haematoxylin and Congo-red. x 300. 



