MUSCULAR SEGMENT OF THE EUSTACHIAN TUBE. 71 



As I regard the layer of tissue between the muscles and the 

 mucous membrane as the submucosa, only a few points require 

 to be mentioned respecting the histology of the muscular seg- 

 ment. If it be desired to obtain a general view of the relations 

 of the voluntary musculus dilatator tubse to the cartilage, 

 transverse sections must be carried through the tuba with its 

 decalcified osseous investment in such a manner that the sec- 

 tions run parallel to the muscular fibres. It may be incontes- 

 tably shown from an examination of such sections, which ought 

 to be rather thick, that the musculus dilatator tubee is attached 

 exclusively to the truncated extremity of the lateral cartila- 

 ginous lamina along the whole length of the Eustachian tube. 

 (See fig. 287.) Its flat tendon limits the submucosa in the 

 tuba of Man, receives transversely striated muscular fibres on 

 its outer side, and coalesces above with the perichondrium of 

 the uncinate extremity. There can be no doubt that in Man 

 the dilatator tubse exhibits no direct transition into the 

 mucous membrane. Even in those cases where it appears as 

 though in the vicinity of the cartilage the muscle is continuous 

 with the mucous membrane, sections demonstrate that an 

 isolated fragment of cartilage is connected with the apex of 

 the hook by means of dense tissue. 



I am able from transverse sections and surface views to 

 corroborate the statement made by v. Troeltsch and L. Mayer, 

 that a direct passage of the musculus dilatator tubse takes place 

 into the tensor tyrnpani, and this is true not only in regard to 

 the tendons, but also for the transversely striated fibres of the 

 two muscles. In Monkeys the muscular segment of the tuba, 

 and especially the musculus dilatator tubse, which is attached 

 exclusively to the truncated extremity of the lateral cartilage, 

 are strongly developed. I have also decalcified the cranial 

 bones of Monkeys, and made transverse sections through the 

 tubse and their investment, and have found that the musculus 

 dilatator tubse does not extend beyond the limits of the lateral 

 cartilage. The muscle holds similar relations to the cartilage 

 in the Pig, Horse, Stag, Reindeer, etc. An exception to this dis- 

 position of parts however occurs in those animals in which no 

 lateral cartilage of the tuba exists, as in the Marmot, Dog, 

 Marten, Otter, and Cat ; in these animals the dilatator tuba? is 



