THE NECK 151 



site of the opening in no way locates the individual cleft which 

 is at fault. Just as the upper arches and clefts leave more normal 

 remains than the lower, so it is found clinically that abnormal 

 remains usually belong to the upper members of the series. 



In the human embryo the cleft membrane never breaks down 

 as it does in fishes, and it is probable that, in cases where a bran- 

 chial fistula is stated to have been complete, the thin cleft 

 membrane has been destroyed by the probe or length of fishing- 

 gut or catgut which has been introduced into the fistula to 

 examine its track. 



This condition can be satisfactorily treated only by dis- 

 secting out the whole track, for, unless this is done, recurrence is 

 certain. An incision is made around the fistulous opening, and 

 it is carried upwards along the anterior border of the sterno- 

 mastoid as far as is necessary. A fine probe, introduced into the 

 fistula as it is being dissected, is found to sink gradually through 

 the superficial fascia and the platysma, and to pierce the deep 

 fascia about the level of the upper border of the thyreoid 

 cartilage. 



In the majority of cases the fistula is derived from the second 

 visceral cleft. Consequently, as it is traced upwards, it will be 

 found to lie superficial to the structures derived from the third 

 and lower arches, e.g. the internal carotid artery and the glosso- 

 pharyngeal nerve, but deep to those developed in relation to 

 the upper two arches. It is therefore crossed by the lingual, 

 occipital, posterior auricular, and external carotid arteries, 

 and by the stylo-hyoid ligament and the hypoglossal nerve. 

 If the fistula extends upwards to the region of the supra-tonsillar 

 fossa or the pharyngeal recess (of Rosenmuller) (p. 190), it will 

 pass between the stylo-hyoid and stylo -pharyngeus muscles, 

 and it has already been explained (p. 149) why the fistula must 

 pass between the two carotid arteries. In order to remove the 

 upper part of the fistula entirely, the probe is pushed through 

 the cleft membrane into the supra-tonsillar fossa or pharyngeal 

 recess, as the case may be. The fistula is then divided, and, 

 after the lower part has been removed, the upper part is attached 

 to the probe and turned inside out by pulling the probe out 

 through the mouth. In this way the whole of the fistula can 

 be completely excised. 



Branchial cysts may be mistaken for enlarged lymph glands, 

 but they only occur singly and are unilateral. They contain 

 a glairy fluid under normal conditions, but if they are infected 



