PLATE 2 



EXPLANATION OF FIGURES 



4 Drawing of the same model as represented in figure 3, with the hypoglossal 

 nerve and a portion of the ganglion nodosum removed to expose the cervical 

 vesicle and more clearly to show its relation to the thymus anlage. Dorso-lateral 

 aspect; reduced one-half. 



5 Drawing of a reconstruction showing the relation of the vesicula cervicalis 

 lateralis (T.s.) to the thymus head (C.t.) and their topographical relation to 

 neighboring structures. In this stage the thymus and the cervical vesicle, which 

 have fused, have lost their connection respectively with the entoderm and ecto- 

 derm. Right side, lateral aspect; pig 21.5 mm. in length. Model X 182, reduced 

 one-half. 



6 Drawing of a reconstruction showing the topographical relation of the 

 superficial thymus to the thymus head. These two structures, in the specimen 

 from which the reconstruction of the thymus was made, are connected with 

 each other by the connecting band (P.i.) which loops over the hypoglossal nerve. 

 Left thymus, lateral aspect. X 30, reduced one-half. 



7 Drawing of model represented in figure 6; ventral aspect. 



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