72 THE EUSTACHIAN TUBE, BY PROFESSOR RUDINGER. 



directly continuous with the dense submucous tissue. In the 

 case of the Horse it is to be remarked that two voluntary 

 muscles, the so-called levator and tensor palatini, are inserted 

 into the lateral part of the cartilage.* 



The musculus levator veil palatini has a peculiar topograph- 

 ical relation to the Eustachian tube, as it ascends from the bot- 

 tom of the tubal fissure in immediate contact with the mucous 

 membrane, as far as to the pars petrosa, where it is attached, 

 not only to the bones, but also, with a few fibres, to the dense 

 submucosa of the mucous membrane. A special transversely 

 striated muscle, which is situated on the median side of the 

 Eustachian tube, occurs in the Stag. It is strongly deve- 

 loped in the Buck, its several fasciculi, surrounded by fat, 

 extending to the median portion of the mucous membrane, 

 with which they are intimately connected, whilst its tendon 

 is continued directly into the fibrous layer of the submucosa. 

 It is destined for the fixation of that part of the mucous 

 membrane which is free from cartilage, and I have named it 

 the dilatator tubse medialis.f 



3. THE Mucous MEMBRANE. 



The mucous membrane of the osseous portion of the Eusta- 

 chian tube, which dips to a variable depth into the inequalities 

 of the osseous surface, varies in diameter between O'OSO and 

 0'112 of a millimeter. Transverse sections of the osseous por- 

 tion of the tuba exhibit no well-defined line of demarcation 

 between the periosteum and the mucous membrane. A finely 

 fibrous nucleated connective tissue is intimately blended with 

 the osseous tissue, and processes are given off from it which 

 dip into the bone. At a little distance from the bone the con- 

 nective tissue becomes somewhat looser in texture, and supports 

 a coarsely meshed vascular plexus, the branches of which are 

 distributed, not only to the mucous membrane, but also in the 

 bone. This layer is remarkably thick on the processes of the bone 

 and at the bottom of the osseous portion of the Eustachian 



* S. Riidinger, Beitrdge zur Anatomie und Histologie der Ohrtrompete. 

 t S. Riidinger, loc. cit., figs. 42 and 43. 



