526 



THE DIGESTIVE SYSTEM. 



The so-called Mycosis pharyngis is apparently due to the growth in 

 susceptible persons of a form of leptothrix not yet thoroughly studied, 

 on account of the technical difficulties in the way of its artificial cultiva- 

 tion. ' 



The Pharynx. 



Malformations. 



BRANCHIAL FISTULA AND CYSTS. When, as not infrequently occurs, the embry- 

 onal gill clefts do not properly close, fistulas may remain. These may in rare cases be 

 complete, so that an opening exists from the pharynx, larynx, or trachea to the side of 

 the neck. More frequently, however, these fistula? are incomplete and shallow, and 



: ,,.-- 



XV^EH*-,^ 



FIG. 303.- SECTION OP THE WALL OF A BRANCHIAL CYST OF THE NECK. 



Formed from the imperfect closure of an embryonal gill cleft. The cyst is lined with ciliated epithelium 

 and the wall is largely formed of diffuse lymphoid tissue. 



open either inward into one of the above-named organs or outward on to the neck. 

 Small portions of the gill clefts may persist without external openings, and from these 

 subcutaneous cysts of the neck are often developed. Or a portion of the cleft may be 

 cut off, forming a cyst, while the fistula persists with its external opening. 



The walls of these fistulae and cysts may be covered with mucous membrane having 

 cylindrical or flattened or ciliated surface cells. Or, when formed from the outer clef us, 

 they may be lined with skin. 



Not infrequently the walls of these cysts and fistula? are embedded in lymphatic 

 tissue, which may be diffuse or gathered in nodular form (see Figs. 303 and 304). 2 



DIVERTICULA of the pharynx have been observed. 



1 For a resume witli bibliography of the bacteria found in the mouth as well as in 

 other parts of the body under normal and pathological conditions, see Mace, " Bacteriol- 

 ogie," 1901, p. 1140. See also Madzoar, Cbl. f. Bak., May 14th, 1902, p. 489. For bac- 

 teria in the mouths of nurslings see Lewkowicz, Arch, de Med. Exp., t. xiii., 1901, p. 633. 



2 For bibliography of branchial cysts and fistulas see Coplin, Proc. Path. Soc. of 

 Philadelphia, new series, vol. iv., p. 109, 1901. 



