654 MANUAL OF HISTOLOGY. 



brane. In the Eiistacliian tube its ciliated cells are of the columnar kind 

 interspersed with beaker cells (Schultze). 



The vascular system of the tympanic cavity is remarkable for present- 

 ing a few very slightly ramifying arterial feeding tubes, forming but a 

 very ill-developed arterial capillary network. The venous portion, on 

 the other hand, is highly developed. Here we meet with considerable 

 vessels forming strong networks. The circulation of the cavity is char- 

 acterised by being very rapid, and subject to small pressure (Prussak). 



The lymphatics of the cavity resemble those of the tympanum (Kessel). 



The nerves require closer attention. On the tympanic branch nume- 

 rous ganglia have been observed, formed of larger or smaller collections 

 of cells, or even of single elements between the medullated fibres (Krause). 

 Numerous nervous networks are also found here. 



The small bones of the ear consist of compact osseous substance, present- 

 ing numerous Haversian canals (Rildinger, Brunner). Between the hammer 

 and ambos only is there a joint. The first of these is covered as far as it 

 is united to the tympanum (i.e.) on its short process, and the so-called 

 handle with a thin coat of hyaline cartilage (Cfruber). 



The union of the short process of the ambos (which is clothed with 

 cartilage) with the side of the cavity is effected by strong connective- 

 tissue, that between ambos and stapes by a symphysis of hyaline cartil- 

 age, with a diaphragm of fibrous tissue in the middle. The cartilaginous 

 borders of the foot of the stirrup, arid of the foramen ovale, are joined by 

 strong connective-tissue (Brunner). 



The muscles of the ossicular auditus are of the striped kind ( 164). 



We conclude this section with a glance at the Eiistacliian tube. 



Its cartilage has been already considered, 108. Its mucous membrane 

 bears a double layer of ciliated epithelium, and contains racemose mucous 

 glands, varying in size and position, however, in diiferent localities. The 

 gland vesicles are lined with columnar cells. The mucous tissue may in 

 parts be infiltrated with lymphoid cells (Riidinger). A nervous plexus with 

 groups of ganglion cells is also to be seen in the Eustachian tube (Krause). 



323. 



The internal, and proper organ of hearing, consists of the vestibule, 

 semicircular canals, and cochlea. The whole is occupied by certain mem- 

 branous bags and canals, containing a watery fluid ; in these the auditory 

 nerves terminate, surrounded by the fluid. The distribution of these 

 nerves is twofold, first, to the ampullae and sacculi of the vestibule, and 

 then to the spiral plate of the cochlea. 



Both the vestibule and internal surface of the semicircular canals are lined 

 with periosteum. The transparent serous fluid with which they are filled 

 is known as the perilymph, or aqunla Cotunii. According to Schwalbe, 

 they may be injected from the subarachnoidal space of the brain through 

 the porus acusticus internus. The periosteum, with the mucous mem- 

 brane of the cavity of the tympanum, constitute the membr. tympani 

 secundaria, resembling in their structure, as a whole, the true drum of the 

 ear in many respects. 



The walls of the saccul'us hemielltpticus and rotundus and c. semicir- 

 cularis membranacei, with their ampulla 3 , suspended in the perilymph, 

 but always attached at definite points to the periosteum, consist of an 

 external undeveloped connective-tissue, composed of stellate corpuscles, 

 and an internal elastic transparent layer, containing numerous nuclei. In 



