180 EVOLUTION AND DISEASE. 
In order to appreciate fully the bearing of these facts 
and some others which will be mentioned, it will be 
necessary to take into consideration the chief points 
connected with the development of the pinna as an 
illustration of the care requisite in interpreting variations 
and abnormalities from the evolutionary point of view. 
The details of the development of the human pinna have 
been carefully described by Professor His. At the end of 
the first month of embryonic life, the first branchial cleft is 
surrounded by six rounded, slightly prominent tubercles, 
“a 
FiG. 95.—Human Ears with so-called supernumerary auricles. 
numbered I to VI in fig. 96, and it is by the coalescence of 
these six tubercles that the pinna is formed. The details 
of their fusion are briefly these :—tubercles I and V 
unite across the fissure and form tragus and antitragus, 
the gap, or notch, between them is represented in the 
adult as the fissura intertragicum ; tubercle VI unites 
with these to form the lobule; tubercle II forms the 
helix, whilst III lengthens out and forms the conchal 
rim and the tail, or cauda helicis, whilst the tubercle 
marked IV becomes the antihelix. 
These facts explain readily enough the mode of origin 
