84 CYSTS. 



ducts, tiil)uli seminiferi, (kc, are constricted by interstitial 

 morbid oTowths : the secretions accumulate : the lono-er this- 

 lasts the more does the original form of the isolated cavity (sc. 

 that of a hollow cylinder) give place to a spherical or spheroidal 

 shape ; a cyst is formed, whose walls are identical with those of 

 the original duct, whose contents are (at least in the earlier 

 stages of the process) identical with the proper secretion of 

 the gland. 



A rare, but on that account all the more interestino; varietv 

 of retention-cysts, is that which originates, not in the ducts of 

 glands, but in the interstitial and intercommunicating lacunae 

 which are loft between the trunk, branches, and terminal papilla* 

 of dendritic vegetations. It does not appear, at first sight, as 

 though these interstitial lacuna were in anywise fitted for con- 

 version into cysts. Not only do they freely communicate with 

 one another, but they are everywhere in such free communi- 

 cation with the external medium, that it would be an abuse of 

 lano'uao'e to si:)eak of orifices, or of a pluo'iiino- of such orifices. 

 This is true, and continues true, so long as a dendritic growth is 

 situated upon a free and level surface. But matters take a diffe- 

 rent turn wlien the growth starts from the inner surfice of a 

 cavity. Take a papilloma protruding from the external os into 

 the vao'ina. A time must needs come when the fjrowth tills the 

 canal of the vagina so completely that its walls begin to exert a 

 lateral reaction upon the tumour; and this counter-pressure 

 must increase in proportion to the bulk of the tumour. The 

 papilla^ are bent towards each other ; their convex surfaces are 

 made to touch ; they ultimately coalesce along the lines of con- 

 tact, and thus convert the open inter -papillary space into a number 

 of minute, tubular crypts which differ from tubular glands ojily 

 by appearing, in transverse sections, to be bounded, not bv 

 circular outlines, but by three or four arcs, convex inwards, ares 

 which correspond to the convex surfaces of the contiguous and 

 coalescent papilla\ These tubes are quite as well adapted as 

 gland-tubuli for the develoj)ment of cysts ; all that is required, 

 indeed, for the occasional closure of one or other of these inter- 

 pa})illary spaces at its external orifice, or at some ])oint in its 

 continuity, being a continued operation of the same external 

 pressure ; and so a retention-cyst is formed. 



This is an excellent opportunity for realising how any accu- 



