30 CROWELL. 



through an incompletely occluded lumen, an empysema rather 

 than a mucocele may result. 



(c) A mucosa able to sec7'ete faster than it can resorb. — This 

 predicates a functionating mucosa, that is, one in which too 

 extensive pathological changes have not been produced by the 

 causative factor upon which the occlusion depends, and unless 

 secretion proceed more rapidly than resorption, dilatation will 

 not occur. Bierhoff is of the opinion that dilatation is wanting 

 when the mucosa is still able to resorb in the usual way. This 

 latter point has been emphasized by several authors, whereas it 

 would seem that in order to prevent dilatation, resorption through 

 the mucous membrane must proceed more rapidly than under 

 normal conditions, inasmuch as the normal outlet into the csecum 

 is occluded. 



The relative infrequency of mucocele in comparison with 

 other lesions of the appendix is thus seen to be accounted for by 

 the stringency of the requisites for its production or the multi- 

 plicity of the factors which must be properly coordinated. 



Occlusion under these conditions having been produced, the 

 changes occurring in the distal portion follow in fairly definite 

 order. The accumulation of retained secretion leads to dilatation 

 and degenerative or atrophic changes in the mucosa and submu- 

 cosa, along with a replacement fibrosis of the tunica muscularis, 

 the fibrosis originating from both the subserous and submucous 

 layers. Some muscular hypertrophy may take place, and if one 

 or more portions of the wall have been unduly weakened by 

 previous disease, for example, ulceration, a diverticulum, or di- 

 verticula may result. The changes in the character of the con- 

 tents depend upon those in the mucosa. A mucoid degeneration 

 of the epithelial elements of the mucosa is a comparatively early 

 feature, leading to over-production of mucus and desquamation 

 of epithelial elements. At this period the contents are thick and 

 mucoid. As the result of the increasing distension, the mucosa 

 undergoes atrophic changes which may involve all or a part of the 

 mucosa according as the previous weakening of the wall has been 

 uniform or otherwise. At the same time the submucosa be- 

 comes replaced by fibrous tissue and the contents become clearer 

 and more watery and of the character of a transudate, which 

 may become turbid and more or less viscid from the admixture 

 of cellular elements from the blood and the desquamated epi- 

 thelium of the mucosa. The pressure may also lead to degenera- 

 tion of a hyaline or myxomatous character in the fibrous tissue. 



The various phases as here depicted form but different stages 



