08 MUCOUS MEMBEANES. 



are subject to similar conditions. Menstruation is associated 

 with clonic contractions of the muscular coat of the uterus. 



Some mucous membranes, however, are not well adapted for 

 the occurrence of hjpergemia. The more abundantly a mucous 

 membrane is provided with elastic fibres, the more does it resist 

 distension bv congestion and oedema; indeed the tendency of 

 tlie membrane to return to its normal volume, increases in pro- 

 }>ortion to the stretching which it undergoes ; this is a necessary 

 result of its elasticity. Many of the phenomena exhibited by 

 the respiratory mucous membrane, which is peculiarly rich in 

 elastic fibres, nmst be ascribed to this cause. Sudden and great 

 swelling onlj- occurs in parts furnished with a very lax sub- 

 nmcous areolar tissue, in the folds about the laryngeal orifice, 

 ])articularly the ary-epiglottidean ligaments, and certain portions 

 of the mucous lining of the nasal cavities. The swelling in such 

 cases howe^•er, is not situated in the mucosa ; it is due to oedema 

 of the submucous connective tissue. It disappears very rapidly 

 as soon as the clastic reaction of the stretched membrane pre- 

 ^•ails over the tension of the dropsical effusion kept up by the 

 blood -pressure ; especially after death, when it is often quite 

 impossible to demonstrate the existence of an oedema, which 

 manifested itself most unequivocally during life, and which may 

 even have been the cause of death (oedema glottidis). 



§ 350. It is obvious that the swelling of the catarrhal 

 mucous membrane, the second anatomical element in this 

 variety of inflammation, depends, at least in some degree, upon 

 the hypera3mia ; i.e. so far as it is due to over-distension of the 

 vessels, and the abundant saturation of the mucous membrane 

 with serum. The latter element is very prominent in all forms 

 of catarrh due to passive congestion ; it is recognised by the 

 bacon}' lustre of the swollen membrane, and by the flow of clear 

 serum from its cut surface. The swelling is much greater when 

 tlie submucous tissue also is involved ; this is most common in 

 the caecum. 



For the pathological histologist, these passive forms of swell- 

 ing are less interesting than the active varieties; i.e. the enlarge- 

 ments of the LYMPHATIC FOLLICLES duc to corpuscular prolifera- 

 tion in their interior. Owing doubtless to the intimate connexion 

 of these glands with the process of absorption, we find catarrh of 

 a mucous surface almost ahvavs associated with a more or less 



