? a7 . “ . hi Links 
eas “ . ; Sh aaleoan 
THE PINNA. 701 
situated below the incisura intertragica, and is the most dependent part of the 
pinna. 
The inner or cranial surface is also irregular and presents elevations corre- 
sponding to the depressions on its outer surface, ¢.g. eminentia conche, eminentia 
triangularis, etc. 
The pinna is usually smaller and more finely modelled in the female than in the male, but 
presents great variations in size and shape in different individuals. In the newly-born child its 
length is about one-third of that of the adult, while it increases slightly in length and breadth 
in old age. 
The relation of the width to the height is termed the auricular index and is expressed 
as follows :— 
width of pinna x 100 : F 
eae —_— — Auricular index. 
ength of pinna 
This index is less in white than in dark races, 
The cephalo-auricular angle may he practically absent, as in those cases where the skin of the 
head passes directly on to the outer surface of the pinna, or it may be increased to nearly a right 
angle, so that the outer surface of the pinna looks directly forwards. The tuberculum superius, 
the significance of which was recognised by Darwin, is a somewhat triangular prominence which 
projects forwards when the helix is well rolled over, but backwards and upwards when the 
incurving of the helix has been arrested. More frequently present in men than in women, it is 
of developmental interest since it has been shown to be well marked at the sixth month of feetal 
life, the entire pinna exhibiting, at this stage, the appearance of that of the adult macaque. 
The lobule may be small and sessile or considerably elongated ; it may adhere to the skin of 
the cheek (webbed) or may tend to bifureate at its lower extremity. 
Structure of the Pinna.—The greater part of the pinna consists of a lamella 
of yellow fibro-cartilage, the cartilago auricule; the cartilage is however absent 
from the lobule, which is composed of adipose tissue. When laid bare, the carti- 
laginous lamella (Figs. 511, 512) presents, in an exaggerated condition, all the in- 
equalities of the pinna, and is seen 
to be prolonged inwards, to form a 
considerable portion of the external 
auditory meatus. The cartilage of — M. helicis major 
the hehx projects anteriorly as a 
conical eminence, the spina helicis, Spina hells 
whilst its inferior extremity ex-  M. helicis minor“ 
tends downwards as a_ tail-like 
process, the cauda helicis, which is Miteceion 1H incisura terminalis 
separated from the lower part of aA Oras 
: Fissure of M. antitragicus 
the antitragus by a fissure, termed Santorini oa pre 
7 Fissura antitragohelicina 
C= Cauda helicis 
the fissura antitragohelicina. The [thmuscartile 
cartilage of the pinna is continuous 
wach that of the AONE. by te Fic. 511.—OvuTer SURFACE OF CARTILAGE OF PINNA 
narrow isthmus (isthmus cartilaginis (one-half natural size). 
auris) measuring from 8-9 mm. in 
breadth. This isthmus corresponds externally with the deepest part of the 
incisura intertragica, and internally it forms the outer boundary of a deep 
fissure, the incisura terminalis auris, which separates the cartilage of the meatus 
from that of the concha. The upper edge of the tragus fits into an angle below 
the crus helicis. 
If the incisura terminalis auris, together with the isthmus and the incisura intertragica, be 
taken as representing the boundary between the cartilage of the pinna and that of the meatus, it 
follows that the tragus really forms a part of the meatal cartilage. 
On the cranial aspect of the cartilage (Fig. 512) the eminences produced by the 
concha and fossa triangularis are separated by a transverse furrow, the sulcus anti- 
helicis transversus, corresponding with the crus antihelicis inferior; further, the 
eminentia conche is crossed horizontally by a groove, the sulcus cruris helicis, and 
almost vertically by a slight ridge, the ponticulus: the latter indicates the attach- 
ment of the retrahens auriculam muscle. 
In addition to the fissures described, others, termed the fissures of Santorini, are 
found, usually one in the tragus and one or more in the cartilage of the meatus. 
