ABBREVIATIONS 



A.c, carotid artery Pi. 3, parathyroid derived from third 



C.t., caput thymus = thymus head pharyngeal pouch 



D.b., ductus branchialis S.fc. :?, sacculus branchialis II = second 



D.c, ductus cervicalis pharyngeal pouch 



Ect., ectoderm S.b.3, sacculus branchialis III = third 



G.n., ganglion nodosum pharyngeal pouch 



G.S.C., superior cervical ganglion S.b.4, sacculus branchialis IV = fourth 



N'.X., vagus nerve ' pharyngeal pouch 



N.XII., hypoglossal nerve T.e., entodermal thvmus 



P., pharynx T.s., thymus superficialis 



P.L, connecting band V.c, vesicula cervicalis 



V.C.I., vesicula cervicalis lateralis 



V.c.m., vesicula cervicalis medialis 



PLATE 1 



EXPLANATION OF FIGURES 



Figures 1 to 7 were drawn by Miss Cora Whitman, from wax models which 

 were made by the author. The text figures A to E were drawn by the author. 



1 Drawing of a reconstruction of the ])harynx and derivatives of the second 

 and third pharyngeal pouches of the right side, including portions of the struc- 

 tures closely associated with the pharyngeal derivatives and a portion of the 

 ectoderm. Ventral aspect; pig embryo 14.5 mm. in length. Model X 92, reduced 

 one-half. 



2 Drawing of a reconstruction of a portion of the pharynx, the third pharyn- 

 geal pouch, anterior portion of the thymus anlage, parathyroid 3, cervical vesicle, 

 and associates of the above named structures. Caudo-ventral aspect. The 

 model represented in this figure was made from the same side of the same em- 

 bryo (14.5 mm.) from which the model represented in figure 1 was made. IVIodel 

 X 245, reduced one-half. 



3 Drawing of a reconstruction of the same structures as enumerated under 

 figure 2. This model was made to show specially the relation of the cervical 

 vesicle to the thymus anlage and the hypoglossal nerve after the shifting of the 

 structures in the neck have become quite noticeable. Ventral aspect, left side; 

 pig embryo 17.5 mm. in length. Model X 182, reduced one-half. 



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