THE NASAL FOSS.<E, PHARYNX, AND TONSILS. 369 



the ciliary current Being invariably toward the choanse (poste- 

 rior nares). It contains, also, goblet-cells. Under the epithe- 

 lium is a true membrana mucosa, which forms at the same 

 time a periosteum for the bones, and is composed almost en- 

 tirely of connective tissue, scantily permeated, if at all, with 

 elastic tissue-elements. The mucous membrane may be divided 

 into two varieties : a thinner membrane, covering the internal 

 surface of the turbinated bones and the accessory sinuses, and 

 the thicker membrane of the nasal fossse proper. 



The thinner membrane contains many acinous glands. In 

 the adjacent cavities they are less abundant, excepting upon 

 the internal wall of the maxillary sinus. Here, and in the 

 sphenoidal sinus, the glands consist of several cylindrical 

 tubes with connecting single oblong acini. The epithelium of 

 the latter is pyriform, while in the tubes it is C3 7 lindrical. The 

 mucous membrane itself is pale in color, and scantily supplied 

 with blood-vessels. Special nerve-terminations have been de- 

 scribed in these sinuses. These are probably nothing more 

 than terminations of fibres from the great sympathetic, having 

 at their extremities ganglionic cellules. 



The thicker membrane covers the lower part of the nasal 

 septum and the inferior and middle turbinated bones. It is 

 lined with the same ciliated epithelium, and in the anterior 

 two- thirds of the turbinated bones forms only a delicate, 

 slightly corrugated covering for the subjacent parts. Poste- 

 riorly, however, its surface is thrown into numerous thick 

 folds, evidently designed to increase the extent of surface of 

 the mucous membrane. 



The membrana mucosa forms a fibrous network, which 

 passes between the glands and vessels and connects the mu- 

 cous membrane with the periosteum. Its characteristics re- 

 semble more nearly those of periosteum, so that it may properly 

 be classed as a part of the latter. The glands of this region 

 vary somewhat from the acinous type, and are composed of 

 tortuous tubules, having many sinuses and oblong offshoots. 

 They are lined on their inner surface with low cylindrical epi- 

 thelium, and sometimes assume a circular, sometimes an oval 

 or tubular shape in the microscopic section. The thickness of 

 the pituitary mucous membrane is due not only to its mucous 

 glands, but more particularly to the existence in it of true erec- 

 tile tissue, as well as venous plexuses. (See p. 160). These are 

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