ORIENTATION OF THE EAR VESICLE 33 



tion. The specimens were fixed after ten days. The results 

 were .as follows : Rotation, 5 ; no rotation, 4 ; lack of criteria, 4 ; 

 no vesicle, 1. 



It is thus demonstrated that the ear vesicles under these condi- 

 tions do not always rotate back to their normal position, even with 

 the same technique used in cases which resulted in rotation. One 

 can hardly assume that this discrepancy is due merely to a differ- 

 ence in the inversion axis, and the explanation must be sought 

 in some other cause. 



On account of the fact that the operation necessitates detaching 

 the skin from the ear vesicle, the latter is usually broken open at 

 its area of closure. If the vesicle is replaced inside out in its 

 pocket, the smooth, intact surface of the original medial side 

 comes in contact with the wound. The skin then grows gradually 

 from all sides of the wound over the vesicle and finally covers it 

 entirely, without any fusion between the two. The matter is differ- 

 ent when the vesicle is replaced upside down. Here the wound of 

 the skin and that of the vesicle come directly in contact. During 

 the process of healing these two wounds may easily fuse with each 

 other. Among Spemann's figures representing the ear vesicles 

 in different stages, there is one which illustrates a vesicle which 

 had just closed, and shows clearly the fusion of skin and vesicle. 

 In explaining this figure Spemann states: ''Die Epidermis zieht 

 zweischichtig iiber das Blaschen hinweg, mit Ausnahme einer 

 nicht ganz regelmassigen Stelle, wo vielleicht noch ein Zusam- 

 menhang zwischen beiden besteht. " 



Although a positive decision can only be obtained by actual 

 study for a number of specimens in early stages, Spemann's 

 figure suggests that this explanation may be the correct one. 



My results and Spemann 's differ as to the percentage of rotated 

 vesicles, Spemann's experiments giving a majority of non-rota- 

 tion. This difference can also be explained by fusion, which is 

 apparently much more favored by Spemann's technique of 

 keeping the wound free. 



