152 THE STRUCTURE OF MAN 
The pinna of the ear deserves special attention. In recent 
years it has been thoroughly investigated by Schwalbe, the results 
of whose researches are here incorporated. This pinna (p., Fig. 90) 
is so elaborately modelled a structure that we can hardly imagine 
it to be degenerate. It undergoes marked variation and adapta- 
tion in different races, tribes, and individuals, as well as at 
different ages. On close examination, variation is found, for the 
most part, to affect those portions of it which stand out freely 
from the head in a postero-dorsal direction. Schwalbe calls these 
parts the “ear-folds,” distinguishing the basal region as the zone 
of the auditory prominence (cf. Fig. 71). 
The pinna of Man arises from six prominences which develop 
near the anterior visceral cleft (au., Fig. 90), and are called the 
branchial auricular prominences. In the adult pinna they are 
still evident as the helix, crus antihelicis inferius, crus helicis, 
tragus, and antitragus (cf. Fig. 71). The human pinna, as 
compared with that of Apes, would appear to be a degenerate 
structure ; and in reality it is much reduced, being rolled over 
in such a way as greatly to modify the upper edge of the helix 
and part of the antihelix. 
The variations of the ear-folds are of great interest, and 
deserve close attention, in connection with the primitive history 
of Man. 
When we examine the highly movable ear of the Ungulata, 
we find that the ear-fold gives rise to a very efficient sensitive 
auditory funnel, which lies parallel to the axis’ of the ear, and 
ends in a free tip (spina). 
In the Primates the pinna is much shortened, and is thrown 
into folds (helix and antihelix) running at right angles to the 
axis of the ear. Schwalbe finds two forms of free tip in the 
Apes. (1) The Macacus or Inuus type (Fig. 71, C); and (2) the 
Cercopithecus type (Fig. 71, D). In the former (C), which some- 
what resembles in shape the ear-fold in human embryos at from 
the fourth to the sixth month, there is a freely developed edge of 
the helix which is not rolled over, and a distinct tip, always in 
the same place. 
From the eighth month, the human ear-fold enters upon a 
degenerative process, which essentially consists in the rolling 
1 By the axis of the pinna (regarded as a standard of measurement) is meant 
a line which connects the true tip of the ear (Woolner’s and Darwin’s tip [spina]) 
with the incisura auris anterior (cf. s.’,s.”,s., Fig. 71, B). By the breadth of the 
organ, in both Man and the lower mammals, is understood the measurement of the 
attached portion (base of the ear). 
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