416 SENSE-ORGANS AND INTEGUMENT. 
culated process (d). This is really part of a transverse ridge, 
extending craniocaudad on the medial wall of the auricular 
cavity. This ridge is the antihelix (d); it divides the auricula 
into a distal and a proximal portion. The portion distad of 
the antihelix is the scapha (a); its surface is smooth except for 
two slight longitudinal ridges extending distad from near the 
two ends of the antihelix. That portion of the auricle that lies 
proximad of the antihelix forms a deep irregular cavity known 
as the concha (¢). A deep furrow, corresponding to the anti- 
helix, separates scapha from concha externally. The concha 
extends caudad as a deep, rounded pocket; externally this 
pocket forms a prominent convexity, the eminentia conche 
(7), on the caudal surface of the proximal portion of the 
external ear. Farther proximad the concha narrows like a 
funnel and becomes much compressed laterally, so that a sec- 
tion of its cavity forms a narrow craniocaudal slit. 
The inner surface of the concha is marked by a number of 
very prominent ridges and projections. These are usually due 
to folds in the cartilage, so that external furrows and depres- 
sions correspond to the internal projections. The edges of these 
depressions serve for attachment of muscles (Fig. 169), by con- 
traction of which the form of the concha is changed, —the folds 
of the cartilage thus serving as regions of greater flexibility. 
Two or three centimeters proximad of its external opening 
the cartilage of the concha ends in a free edge which receives 
within itself the distal end of the cartilaginous external auditory 
meatus (¢’). The two are united together by fibrous tissue. 
The cartilaginous auditory meatus (e’) extends as a nearly 
cylindrical tube mediad and slightly craniad to the tympanic 
membrane in the opening of the bulla tympani. This tube is 
lined with integument which continues over the tympanic 
membrane. The subcutaneous tissue of the tube contains the 
ceruminous glands, which secrete the ear-wax and open on the 
surface of the skin. ? 
To understand the relations of the muscles of the external 
ear it is necessary to consider a little more fully the structure 
of the auricular cartilage (Fig. 168), especially as compared 
with the human ear. The ear of the cat differs from the human 
