TRANSMISSION OF MALFORMA TIONS. 1 8 1 



of the various congenital defects of the pinna. Thus a 

 fistula in the helix results from incomplete coalescence 

 of the tubercles II and III, whilst a fistula in the lobule 

 represents a gap between the tubercles I, V, and VI. The 

 furrow in the lobule is a fault where the lobule comes 

 into relation with the tail of the helix. Should any of 



FIG. 96. A, the six tubercles surrounding the first cleft ; B, an 

 intermediate stage in the coalescence of the tubercles. C, a 

 still later stage. (After His.) 



the tubercles fuse superficially and leave an intermediate 

 space, this may subsequently dilate and form what is 

 known as a dermoid cyst that is, a tumour with a central 

 cavity lined with skin resembling that covering the 

 pinna. 



These facts are of some importance because, with an 



