THE PHARYNX AND (ESOPHAGUS. 79 



former ^ — 1'" in diameter, have distinct apertures and abound 

 more particularly in the upper portions of the pharynx, where 

 they form a perfectly continuous layer on the posterior wall, in 

 the neighbourhood of the pharyngeal opening of the Eustachian 

 tubes, and upon the posterior surface of the velum, diminishing 

 in number lower down. Follicular glands, simple as well as 

 compound, analogous to the tonsils, are met with in the vault 

 of the pharynx, where the mucous membrane is closely attached 

 to the base of the skull. Here a glandular mass, stretching from 

 one Eustachian opening to the other, and from one to four 

 lines thick, may constantly be met with ; it is, upon the whole, 

 smaller, but otherwise its structure resembles, in all essential 

 respects, that of the tonsils (§ 135). Besides this mass, whose 

 largest sacculations are situated in the middle of the roof of the 

 pharnyx, and in the recesses behind the Eustachian apertures, 

 and which, in aged persons, frequently present enlarged cavities, 

 filled with puriform masses, there occur round the apertures of 

 the tubes, and upon them, towards the choance, on the posterior 

 surface of the velum palati, and on the lateral walls of the pha- 

 rynx, as far as the level of the epiglottis, more or less numerous, 

 smaller and larger follicles, whose size is too great for apertures 

 of the mucous glands, and which have in all probability the 

 same structure as the simple follicles of the root of the tongue, 

 and receive the excretory ducts of the mucous glands. 



The mucous membrane of the pjharynx is rich in blood- 

 vessels and lymphatics. The former constitute superficially a 

 network with elongated meshes, sending short loops into the 

 rudimentary papillae. The nerves are very numerous, form 

 superficial and deep plexuses, the former with fine fibres of 

 O001 — -0015'", which occasionally divide, and whose ultimate 

 terminations escape the eye. 



2. THE (ESOPHAGUS. 



§ 145. 



The wall of the oesophagus, 1± — If" thick, consists, externally, 

 of a fibrous membrane composed of connective tissue, with ex- 

 ceedingly beautiful elastic fibres. To this succeeds a muscular 



