TRANSMISSION OF MALFORMATIONS. 181 
of the various congenital defects of the pinna. Thus a 
fistula in the helix results from incomplete coalescence 
of the tubercles IIT 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 
Fic. 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 
