80 



SPECIAL HISTOLOGY. 





membrane | — 1'" thick, composed of an external, longitudinally 



fibrous layer, having a thickness of 0*5'", and of an internal, 



circularly fibrous layer of 0*24 

 Fig- 198. ^o/// 1.- -u • 1 



, — 0*3 , which are m close ap- 



-y position. From the pharynx, 

 f* where the longitudinal fibres 

 arise in two bundles from the 

 constrictor infimus, united with 

 a third from the cricoid car- 

 4 tilage, they extend as far as the 

 d stomach, with whose muscles 

 they are partly continuous. In 

 the upper third of oesophagus, 

 as far as its entrance into 

 the thorax, transversely striated 

 muscles alone are found, ar- 

 ranged in bundles of 004 — 

 024"' ', which sometimes dis- 

 tinctly anastomose. Further 

 downwards smooth muscles of 

 the same structure as those in 

 the intestine (infra) make their 

 appearance, in the first place 

 in the circular layer and subsequently, among the longi- 

 tudinal fibres; the proportion of these gradually increases, 

 until at last, in the lower fourth, smooth muscle altogether 

 predominates. Isolated, transversely-striated muscles, however, 

 are, according to Ficinus, to be met with as far as the cardia. 

 Most internally we find, separated from the muscular coat 

 by a white, soft layer of submucous connective tissue {tunica 

 nervea of the ancients), the pale-red mucous membrane, which 

 below takes on a whitish tint. Its total thickness 0-36"' — 

 0-45'" is due, to the extent of about 01 — 0*1 2'", to its 

 laminated, tesselated epithelium, which presents the same 

 structure as in the oral cavity, with the exception, however, 

 that the actual epithelial plates constitute about a moiety of 



Fig. 198. Transverse section from the middle of the oesophagus (Man), x 1 — 2 : a, 

 fibrous investment ; b, longitudinal muscles ; c, transverse muscles ; d, tunica nervea ; 

 e, longitudinal muscles of the mucous membrane ; /, papillae ; g, epithelium ; h, aper- 

 ture of a mucous gland ; i, mass of fat. 



