34 CROWELL. 



ably of the same nature as those described in Stengel's case 

 and do not, to my mind, furnish evidence of tumor formation. 

 The number of leucocytes associated with the exfoliated epithe- 

 lium is remarkable. In no place in the appendix is there 

 anything suggesting invasion of the muscularis by epithelial 

 elements. In the appendix where the mucosa is lacking, the 

 lining fibrous tissue has undergone a myxomatous transforma- 

 tion, being represented by but few cells and abundant trans- 

 parent, homogeneous, intercellular substance. In the wall 

 adjacent to the point of formation of the cyst there is evidence 

 of an old haemorrhage. 



This case exemplifies one mode of formation of both muco- 

 celes and diverticula. The preexisting inflammation, upon 

 which the occlusion of the orifice depended, was also responsible 

 in all probability for some of the destruction of the mucosa as 

 well as for the almost complete destruction of the wall at one 

 point which made possible the formation of the cyst. The 

 degenerative and atrophic changes were natural sequelae. Had 

 the constriction in the middle third been more nearly imper- 

 meable, then a second cyst would have developed involving the 

 distal third. Had the condition persisted for a greater length 

 of time, the character of the contents would have been changed, 

 the wall would have become thin and transparent, and the cyst 

 much larger. 



Plate 2 is a semidiagrammatic drawing of a section stained 

 by Van Gieson's method, designed to show the method of for- 

 mation of the diverticulum as well as the mucocele. 



SUMMARY. 



1. A mucocele of the appendix is a retention cyst, the requi- 

 sites for the production of which are: 



a. Gradual occlusion of the lumen. 



b. Absence of infection with pyogenic organisms. 



c. A mucosa able to secrete faster than it can resorb. 



2. The infrequency of the association of these factors ac- 

 counts for the rarity of mucoceles. 



3. They are of inflammatory origin, no case indubitably of 

 intrinsic tumor formation having been recorded. 



4. The terms hydrops and mucocele are used interchangeably, 

 but it would seem preferable to apply the terms to different 

 stages of the same process. 



5. Diverticula of the appendix not infrequently occur in the 

 formation of mucoceles. 



