452 MEATUS AUDITORIUS EXTERNUS. 



man, than in any other animal ; and that the lobus is peculiar 

 to the human ear. 



The Meatus Auditorius Externus is a tube, extending 

 from the concha to the membrana tympani, the external 

 extremity of which is principally composed of cartilage, and 

 the internal of bone. The cartilage in the external portion of 

 the tube is a continuation of.the substance of the concha. It 

 does not solely form a complete tube, for, when the meatus is 

 opened longitudinally and spread out, this cartilage appears 

 triangular in shape ; a fibrous membrane being joined to it to 

 complete the tube. 



In addition to the deficiency thus arising, there are two others, 

 one of which, that has a transverse position, is of considerable 

 size. These deficiencies are called Incisurce ; and the fibrous 

 structure which closes that which is transverse, has been called 

 by Santorini, who described it, Musculus Incisura Majoris. 



The cartilage is attached to the bony portion of the meatus 

 at the lower part of its margin, and forms about one half of the 

 length of the meatus. 



The skin covering the external ear is continued into the 

 meatus, and lines it throughout ; extending over the incisurae, 

 and also over the membrana tympani. It adheres more firmly 

 to the periosteum of the bony part of the meatus than to any 

 other portion of the canal. Some fine hair is often observa- 

 ble growing out of it at the external extremity. As the skin 

 advances deeper in the meatus it becomes more and more 

 delicate and sensible. The extreme pain excited by the pene- 

 tration of an insect, or the introduction of an instrument, into 

 the ear, evinces the great degree of sensibility with which it is 

 induced. 



Exterior to the skin, in the cellular membrane which sur- 

 rounds it,- are many small glands* of a yellowish color, whose 

 ducts open upon the surface of the meatus, and pour upon it 

 the substance called cerumen or ear-wax. These glands are 

 most numerous about the middle of the meatus and at those 



* Discovered by Stenon, in 1662. p. 



